Technical Report
SECRC/RDPT/ELD-2012/xxx
Corporate Research
Issued by department
ZCRD/SECRC/RDPT/ELD
Last edit date
Lang.
Revision
2012-05-24
Eng
01
Classification
Normal
Customer
Doc. title
Upgrade of PV Lab and Implementation of Automatic Measurement System
Project name/ID
(Thesis Report)
Status of document
Final
Main Author
Yasir Karim Qureshi
Project ID (CRID)
—–
Additional Author(s)
Page
1/46
CR Program
Distribution
Keywords
DAQ system, PV Lab, Measurement System
Attested by Reviewer
Panagiotis Bakas (ABB), Mikael Ekström (MdH)
Approved by
Georgios Demetriades (ABB), Lars Asplund (MdH)
Final Approval Date
2012-06-02
Summary:
This report is focused on the implementation of a data acquisition system that will be used for
measuring different parameters which are needed in solar panel behavior analysis. To accomplish the DAQ system a DAQ board has been designed and implemented. This DAQ board acquires measured climatic parameters that affect the PV module behavior and voltage and current
of a PV module. The DAQ board may take measurements of multiple analog and digital signals
that come from various sensors including solar radiation, temperature, wind sensors and other
measurement devices. The DAQ board may also output analog signals for controlling other devices.
The DAQ board is the basic part of the DAQ system and several of them can be connected via
a single communication bus (RS485). A unique slave ID can be assigned to each DAQ board on
the communication bus, which allows the control of all boards via a GUI application installed on
a master computer. Therefore, the DAQ system can be used for monitoring a PV module installation as well as logging the measured data in a data storage server.
This report outlines the details of the DAQ system design which are helpful in utilizing or upgrading this system. These details also include programming of DAQ board and implementation
of MODBUS communication protocol within the DAQ system.
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
Corporate Research
SECRC/RDPT/ELD-2012/xxx
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
2/46
CONTENTS
1 Introduction
6
1.1 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6
1.2 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6
1.3 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6
1.4 Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7
2 Problem Description
8
3 Requirements
8
3.1 DAQ board Hardware Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9
3.1.1 Multiple sensors input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9
3.1.2 Discrete signals input/output . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9
3.1.3 Analog signals input/output . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9
3.1.4 Filtering and Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9
3.1.5 Communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9
3.1.6 Trackability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.1.7 PCB size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.2 MODBUS Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.3 Firmware Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.3.1 Slave ID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.3.2 Serial Peripheral Interface (SPI) . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.3.3 External Discrete Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.3.4 Electro-mechanical Relays - Discrete Outputs . . . . . . . . . . . . . . . . . . . 10
3.3.5 MODBUS protocol compatibility . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.4 GUI Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4 Solution
12
4.1 Hardware Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
4.1.1 Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
4.1.2 Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
4.1.3 Communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
4.1.4 Programmability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
4.2 Technical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
4.3 Hardware Design Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
4.3.1 Inter-device Communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
4.3.2 External Communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.3.3 Built-in Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.3.4 In System Programming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
Corporate Research
SECRC/RDPT/ELD-2012/xxx
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
3/46
4.3.5 Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
4.3.6 PCB size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
4.4 Software Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
4.5 MODBUS (MB) Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
4.5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.5.2 General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.5.3 Communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
4.5.4 Request and Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
4.5.5 PDU Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
4.5.6 Data Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
4.5.7 MB Data Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
4.5.8 Function codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
4.5.9 Further Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
4.6 Firmware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
4.6.1 Slave ID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
4.6.2 I/O Components Mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
4.6.3 Data Allocation and Addressing . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
4.6.4 Flow Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
4.6.5 Serial Port (RS-485) Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.6.6 Source Code Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
4.6.7 Programming Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
4.7 GUI Application Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
4.7.1 GUI General Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
4.7.2 GUI Application Usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
4.7.3 Flow Diagram of GUI Application . . . . . . . . . . . . . . . . . . . . . . . . . . 33
4.7.4 Source Code Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
4.7.5 Programming Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
4.8 Example MB Request/Response Messages . . . . . . . . . . . . . . . . . . . . . . . . . 35
4.8.1 Example 1 “Reading Coils” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
4.8.2 Example 2 “Reading Input Registers” . . . . . . . . . . . . . . . . . . . . . . . . 36
4.8.3 Example 3 “Writing Holding Registers” . . . . . . . . . . . . . . . . . . . . . . . 37
5 Results
38
5.1 ADC test results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
5.2 Results with GUI application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
5.3 Data Logging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
5.4 Data Manipulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
6 Conclusions
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
41
Technical Report
SECRC/RDPT/ELD-2012/xxx
Corporate Research
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
4/46
7 Future Work
41
8 REFERENCES
42
9 Enclosures
44
A Schematic and PCB of DAQ Board
45
A.1 Schematic of DAQ Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
A.2 PCB Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
A.3 PCB images of DAQ Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
B Software for DAQ system
45
B.1 Firmware for Server (Source Code) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
B.2 Software for Client (MATLAB files) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
CHANGE HISTORY
46
REVIEW HISTORY
46
LIST OF TABLES
1
Definitions of typical terms and abbreviations . . . . . . . . . . . . . . . . . . . . . . .
6
2
Technical specifications of DAQ system board . . . . . . . . . . . . . . . . . . . . . . . 13
3
Enclosure size for DAQ board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
4
MB Data Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
5
Public Function Codes Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
6
I/O Components Mapping as MB Data Model . . . . . . . . . . . . . . . . . . . . . . . 27
7
The memory locations on DAQ board . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
8
Serial Port Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
9
Tools used for the Firmware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
10
Example 1 (Reading coils) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
11
Example 2 (Reading Input Registers) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
12
Example 3 (Writing Holding Registers) . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
13
ADC Test Result . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
LIST OF FIGURES
4.1 DAQ board with labels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
4.2 SPI port utilization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.3 Pin connections at PORTD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.4 Pin connections at USART port
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.5 Connections at ADC (U2) channels 6 and 7
. . . . . . . . . . . . . . . . . . . . . . . . 17
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
Corporate Research
SECRC/RDPT/ELD-2012/xxx
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
5/46
4.6 ICSP port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
4.7 UL PC 200/63 HT with DAQ system board . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4.8 Communication between DAQ boards and Computer . . . . . . . . . . . . . . . . . . 20
4.9 MB Communication Stack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.10 General MB ADU Frame . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.11 Function code and Data block relation . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
4.12 MB transaction without errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
4.13 MB transaction with errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
4.14 MB Function Code Categories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
4.15 DIP Switches for Slave ID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
4.16 Data Allocation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
4.17 Flow Diagram of DAQ board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.18 MPLAB IDE v8.66 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
4.19 GUI Application’s Window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
4.20 Flow Diagram of GUI Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
5.1 Response from DAQ board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
5.2 Preview of DAQ_dev_001.txt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
5.3 MATLAB’s Command Window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
9.1 Prototype of DAQ board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
SECRC/RDPT/ELD-2012/xxx
Corporate Research
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
6/46
1 INTRODUCTION
1.1 Purpose
The purpose of this report is to explain the building blocks of a data acquisition (DAQ) system
along with complete hardware and software details. The wiring and connection diagrams related
to the DAQ board may also be helpful in redesigning the board. Note that the DAQ board works
as slave/server and is specifically designed to gather data from outdoor sensors.
1.2 Scope
This report describes the hardware architecture and the programming of DAQ system in detail.
The report covers the following main topics related to the DAQ system:
• Technical specifications and hardware design of the DAQ board,
• MODBUS protocol implementation within the DAQ system,
• Programming of a single DAQ board (Firmware)
• GUI application software for the master computer
• Tools for programming the DAQ system
This report can be utilized to understand and implement the specific DAQ system. The report
describes both the Hardware and Software for the DAQ system. The report does not describes
the installation of the DAQ system with PV modules.
1.3 Definitions
Table 1: Definitions of typical terms and abbreviations
ADC
DAC
ADU
PDU
CRC
Communication
Protocol
D-sub
DAQ
DIP
Analog to Digital Converter
Digital to Analog Converter
Application Data Unit, a term used in MODBUS protocol to
describe structure of a single MODBUS message.
Protocol Data Unit, a term used in MODBUS protocol to
describe packet of bytes within ADU for function code and
data.
Cyclic Redundancy Check. It is a technique to check accuracy
of received data at master or slave terminals.
In general, a set of rules determining the format and
transmission of data in a system.
D-subminiature, a common type of electrical connector
named for their D-shaped structure of metal shield
abbreviation used for Data Acquisition
Dual In Package
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
Corporate Research
SECRC/RDPT/ELD-2012/xxx
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Firmware
I/O
IDE
ICD3
ICSP
IP Rating
LED
LSB
MSB
Master device
Slave device
MB
Op-Amp
OSI model
PCB
PLCC
Port
PV
RS-232
RS-485
SMT
SPI
USART
Xtal
Page
7/46
Software (programs or data) that has been written onto
read-only memory (ROM). Firmware is a combination of
software and hardware.
input / output
Integrated Development Environment
In-Circuit Debugger 3[5]
In-Circuit Serial Programming[1]
Ingress Protection Rating
Light-emitting diode
Least Significant Bit
Most Significant Bit
client device or a device with command user interface
server device or a device responsible to respond the requests
of master device
abbreviation used for MODBUS
Operational Amplifier
Open Systems Interconnection model. This is the
communication standard for computer networking in terms of
abstraction layers.
Printed Circuit Board
Plastic Leaded Chip Carrier
A set of I/O pins which are used for sending or receiving binary
data. The port may be a part of any microcontroller or a device
board. A simple microcontroller may have one or more than
one port and each port can be a set of various (normally 8) I/O
pins.
Photovoltaic
A standard defining the electrical characteristics and timing of
signals for serial communication between 2 devices within
short range.
A standard defining the electrical characteristics of drivers and
receivers for use in balanced digital multipoint systems with
long range.
Surface Mount Technology
Serial Peripheral Interface[2]
abbreviation for Universal Synchronous Asynchronous
Receiver Transmitter is an individual or (part of an) integrated
circuit used for serial communications over a computer or
peripheral device serial port.
term used in electronic schematics, short for Crystal
1.4 Structure
This report has the following structure:
Introduction Section 1, (this section) describes the purpose and scope for this report as well as
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
Corporate Research
SECRC/RDPT/ELD-2012/xxx
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
8/46
terms, abbreviations and acronyms used.
Problem Description Section 2, describes the issues that need to be addressed by the DAQ system.
Requirements Section 3, provides necessary information about the requirements that need to
be taken into account when designing and implementing the DAQ system.
Solution Section 4, provides the description of the solution, thus the design and programming
process of the DAQ system. This also includes GUI application software for the master
computer and MODBUS protocol implementation within the DAQ system.
References Section specifies source material for further reading.
Enclosures section 9 provides supplementing information.
2 PROBLEM DESCRIPTION
Sunlight is one of the freely available resources of energy and Photovoltaic (PV) Modules have
made it possible to convert that energy to electricity. PV Systems have greatly gained the attention
of power generation industry. Although PV Modules are functioning properly but their behavior
under outdoors operating conditions is still matter of research. Therefore, in order to study the
behavior of PV modules in real time situation, an embedded device capable of operating outdoor is needed. The basic purpose of this device would be to acquire data from various outdoor
sensors including PV module voltage and current and transmit this data to a remote computer
system. Such functionality makes this system so called “Data Acquisition System”. Several such
DAQ boards could be installed along with PV modules to log data that can be used for analyzing the performance of PV system under different climatic conditions. In addition, it should be
pointed out that the DAQ board should be kept safely enclosed and unaffected by weather conditions.
Along with this, the DAQ board will also need a system software (firmware) to make it fully functional and controllable. The system software would initialize and enable all the features of the
DAQ board. The DAQ board would be designed specifically for outdoor usage, and all the DAQ
boards will share the same bus to communicate with the master computer. In order to have a
good transmission of data from multiple sources on the single bus, the DAQ system would require a communication protocol like MODBUS protocol to ensure error free data transmission
between the master computer and the slave DAQ boards. A GUI application for the master computer should also be developed in MATLAB software. This would allow the user to control several slave DAQ boards through the master computer by using their unique IDs assigned for the
same communication bus. The firmware for the DAQ boards and GUI application for the master
computer would enable the DAQ measurement system to function properly in an user friendly
manner.
3 REQUIREMENTS
The DAQ system is an automatic measurement system and is split in two major parts, Hardware
and Software. The hardware part includes the design of the DAQ board which would be installed
outdoor along with PV modules. The software includes the programming of the DAQ boards
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
Corporate Research
SECRC/RDPT/ELD-2012/xxx
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
9/46
(firmware) and GUI application software for the master computer which would be operated in
an indoor location remote from the PV modules and the DAQ boards. The slave DAQ boards
and the master computer should communicate over RS-485 serial bus using MODBUS protocol.
In order to properly implement the DAQ system, several hardware and software requirements
should be fulfilled, which are described in the following sections.
3.1 DAQ board Hardware Requirements
In order to be flexible, the DAQ board must possess the following capabilities:
3.1.1 Multiple sensors input
The device must be capable of gathering analog data from multiple sensors quickly and efficiently. Thus, several analog inputs should be included on each DAQ board in order to allow the
measurement of multiple signals per DAQ board.
3.1.2 Discrete signals input/output
The device must be capable of reading as well as outputting discrete signals. The discrete signals
should not damage the device in case if high voltage (more than 5 volts) is observed as input.
Discrete outputs may be utilized to turn on/off electromechanical relays.
3.1.3 Analog signals input/output
The device must be capable of reading as well as outputting analog signals. The analog signals as
input should also be passed through the filter in order to be protected against high voltages (more
than 5 volts). The analog signals then should be processed and converted to digital in 12-bit or
higher resolutions. The analog signals as output can be used for digital calibration of actuators
and solar trackers.
3.1.4 Filtering and Protection
The DAQ board would be connected to various sensors externally to acquire environmental data.
Thus, it is required to integrate filtering circuit at the inputs of the DAQ board in order to protect
it from unexpected high voltage (more than 5 volts) signals.
3.1.5 Communication
Long range: As the device would be used to acquire data from outdoor sensors, it must be capable of communicating with a remote computer system in the range of 1m to 1km.
Multipoint: The device must be capable of communicating with other interconnected devices
on a common bus. This would reasonably decrease the overhead due to number of cables for all
the devices.
Inter-device: Communication with add-on components on the device should also be possible
through commonly applied standard interfaces like SPI[2]. SPI is a common communication
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
Corporate Research
SECRC/RDPT/ELD-2012/xxx
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
10/46
standard which is used by a number of ADCs and DACs. Along with this, one SPI port for external
communication would also make this device flexible enough to connect with add-on SPI devices.
3.1.6 Trackability
The device must be capable of being uniquely identified and tracked over the serial communication bus. Manually assignable slave ID number through DIP switches would be a good option.
3.1.7 PCB size
The dimensions for PCB of the device must be compatible with readily available enclosures. This
will allow the device to be protected for safe outdoor operation.
3.2 MODBUS Protocol
MODBUS protocol would be used for common communication between DAQ boards and the
master computer within the DAQ system. In order to implement MODBUS protocol, a set of
MODBUS drivers for both computer and the DAQ boards are required.
3.3 Firmware Requirements
The firmware developed for a single DAQ board should work the same on all the other identical
devices. The DAQ board should work as a slave device and respond to the requests sent by the
master computer. The DAQ board should also be capable of restarting itself in case of not having
proper response.
3.3.1 Slave ID
The slave ID would be useful in tracking each DAQ board over RS485 serial bus. All the DAQ
boards would possess a set of eight DIP switches which would be used to set their IDs. The
firmware should be capable of acquiring the ID through these dip switches.
3.3.2 Serial Peripheral Interface (SPI)
The ADC and the DAC chips on the DAQ board would use SPI port to communicate with the
microcontroller. Thus the firmware should be capable of handling SPI communication.
3.3.3 External Discrete Inputs
The DAQ boards would be capable of accepting some external discrete inputs from other devices.
The firmware should be able to acknowledge these inputs.
3.3.4 Electro-mechanical Relays - Discrete Outputs
The DAQ board would possess electro-mechanical relays which should be controllable (turned
ON or OFF) from the computer.
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
Corporate Research
SECRC/RDPT/ELD-2012/xxx
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
11/46
3.3.5 MODBUS protocol compatibility
The I/O components of the DAQ board should be carefully mapped to the MODBUS data model
which will ensure the MODBUS protocol compatibility.
3.4 GUI Application
The GUI application should be programmed in MATLAB software and it should provide all the
necessary functions for acquiring every possible information from the DAQ boards to the user of
the master computer.
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
SECRC/RDPT/ELD-2012/xxx
Corporate Research
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
12/46
4 SOLUTION
Solution to all the specified hardware requirements is the DAQ board which is based on the results from a previous group project[3]. The DAQ board is shown in figure 4.1,
Figure 4.1: DAQ board with labels
4.1 Hardware Overview
The DAQ board is a multipurpose monitoring device which can not only acquire analog data
from various sensors but also allows to control actuators through electromechanical relays. The
board includes the following functional capabilities:
4.1.1 Inputs
#
Input
01
Analog Signal
02
PT100
03
Discrete signal
04
High voltage
05
06
Unit/Type
Level/Range
Quantity
Label (fig. 4.1)
voltage
0 ... 5V
12
9
resistance
1 ... 400Ω
2
10
voltage
2 ... 10V
4
7
voltage
1 ... 1kV
1
12
High Current
current
1 ... 25A
1
11
DIP switch
Tag / ID
0 ... 255
1
3
#
Output
Unit/Purpose
Level/Range
Quantity
Label (fig. 4.1)
01
Analog Signal
voltage
0 ... 4.095V
2
13
02
Relay
switching
ON / OFF
4
8
4.1.2 Outputs
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
SECRC/RDPT/ELD-2012/xxx
Corporate Research
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
13/46
4.1.3 Communication
#
Standard
Bus
Type
Range
Label (fig. 4.1)
01
RS-485
serial
1-to-many
1m...1km
2
02
RS-232
serial
1-to-1
1m...15m
5
03
SPI[2]
serial
1-to-many
3m
6
Source
Type
Debugging
Label (fig. 4.1)
4.1.4 Programmability
#
Method
01
ICSP[1]
ICD3
default
yes
4
02
Bootloader
RS-232
optional
no
5
4.2 Technical Specifications
The technical specifications of the DAQ board are listed in table 2, where all the major hardware
components (including I/O components) are listed. The labels for components as mentioned
in table 2 are same as the labels on PCB of the DAQ board presented in appendix A.3. The details about various hardware components can be found in referenced datasheets, as outlined in
table 2. Moreover, the details about supplementary hardware components can be found on the
schematic design in appendix A.1.
Table 2: Technical specifications of DAQ system board
Category
Microprocessor
Components
Description
1x PIC16F877 [4]
- High performance, 44-pins, PLCC package,
- 20 MHz clock input, 200 ns instruction cycle,
- Pinout compatible to other 44-pin 16C & 16F series,
- USART, SPI and I2 C on-chip Serial Ports
Label on PCB:
U1
ADC
DAC
Communication
Relays
2x LTC1290 [6]
- 8+8 Single-Ended Inputs, Uni/bi-polar functionality,
- 12-Bit Resolution, SPI interface, 13µs conversion time,
Labels on PCB:
Linked connectors:
U2
INPUT-CON-01 (quick connector)
U3
INPUT-CON-02, INPUT-CON-03 (quick connectors)
1x LTC1446 [7]
- Dual channels output, 12-Bit Resolution,
- SPI interface, 14µs Settling time, Power-on Reset
Label on PCB:
Linked connector:
U9
CON-03 (quick connector)
1x MAX232 [8]
- Dual EIA-232(UART) Driver/Receiver
Label on PCB:
Linked connector:
U4
D-SUB9 (male connector)
1x MAX485 [9]
- RS-485/RS-422 Transceiver
Label on PCB:
Linked connectors:
U5
CON-01 and CON-02 (quick connectors)
4x V23092A [10]
- Slimline PCB Relay SNR, Single pole form A(NO)
Labels on PCB:
Linked connectors:
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
Corporate Research
SECRC/RDPT/ELD-2012/xxx
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Optocouplers
Sensor
Voltage
Regulators
Other Ports
Page
14/46
SNR-01
RELAY-CON1 (MSTBA3, phoenix connector 5.08mm pitch)
SNR-02
RELAY-CON2 (MSTBA3, phoenix connector 5.08mm pitch)
SNR-03
RELAY-CON3 (MSTBA3, phoenix connector 5.08mm pitch)
SNR-04
RELAY-CON4 (MSTBA3, phoenix connector 5.08mm pitch)
4x TIL111M [11]
- General purpose 6-Pin phototransistor Optocouplers
Labels on PCB:
Linked connectors:
OPTC1
CON-05 (quick connector)
OPTC2
CON-06 (quick connector)
OPTC3
CON-07 (quick connector)
OPTC4
CON-08 (quick connector)
1x LA 25-NP [12]
- Current transducer, Closed loop Hall Effect sensor
Label on PCB:
Linked connector:
LA25
PCON (MKDSN1, phoenix connector 5.08 pitch ) @ Iin
1x LM7805 [13]
- Supplies regulated 5V to on-device components.
Label on PCB:
Linked connector: (source input)
U14
CON-01 and CON-02 (quick connectors)
1x LT1027 [14]
- Supplies regulated 5V for referencing.
Label on PCB:
Connected ADCs:
U12
U2 and U3
1x RJ-11 6-pole
1x Micromatch 6
- dedicated to ICSP only, (@ ICSP)
- Available for add-on devices with SPI link, (@ CON_SPI)
4.3 Hardware Design Considerations
The core element of the DAQ board is the PIC16F877A[4] (44-pin, PLCC package) microcontroller
which controls the data acquisition and performs all the communication operations. However,
additional hardware devices are needed for interfacing the microcontroller with measurement
sensors and other external devices. Such hardware perform the reading of analog signals or generation of analog control signals.
4.3.1 Inter-device Communication
The PIC16F877A microcontroller can communicate with other hardware components either by
using any built-in standard communication port (like SPI, I2 C, USART etc) or by directly using
I/O pins. For efficient use of available I/O pins, the SPI port is utilized as common port for interdevice communication with ADC and DAC chips along with equal number of I/O pins for enabling or disabling the respective chips. Figure 4.2 shows utilization of SPI port along with enable/disable I/O pins on the DAQ board.
The discrete signals on other hand are constant signals (in the range of 0 to 5 volts where 0V =
OFF and 5V = ON) which result from any push button or as an actuation response from other
devices. The discrete signals on the DAQ board are treated indirectly through I/O pins at PORTD
of the microcontroller and no standard communication port is used.
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
SECRC/RDPT/ELD-2012/xxx
Corporate Research
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
15/46
Figure 4.2: SPI port utilization
RB2 (38)
/CS (15)
(ADC)
LTC1290
Slave
RC3/SCK (20)
RC4/SDI (25)
RC5/SDO (26)
SCK (18)
DOUT (16)
DIN (17)
U2
(ADC)
RB3 (39)
/CS (15)
LTC1290
Slave
PIC16F877A
SCK (18)
DOUT (16)
DIN (17)
Master
RB1 (37)
/CS (3)
U3
(DAC)
LTC1446
Slave
SCK (1)
DIN (2)
U9
External discrete signals (resulting from push buttons or actuator response) at the input (CON-05,
CON-06, CON-07 and CON-08) are isolated from I/O pins of the microcontroller through optocouplers to protect the microcontroller from high voltages and different grounding. Internally, discrete signals operate on transistors for switching the relays (SNR-01, SNR-02, SNR-03 and SNR-04)
of the DAQ board.
/EN (19)
U6
RD0 (21)
RD1 (22)
RD2 (23)
RD3 (24)
RD4 (30)
RD5 (31)
RD6 (32)
RD7 (33)
A0 (02)
A1 (03)
A2 (04)
A3 (05)
A4 (06)
A5 (07)
A6 (08)
A7 (09)
B0 (18)
B1 (17)
B2 (16)
B3 (15)
B4 (14)
B5 (13)
B6 (12)
B7 (11)
74HC245
RA0 (03)
Dip Switches
Figure 4.3: Pin connections at PORTD
PIC16F877A
RA2 (05)
1A0 (02)
1A1 (04)
1A2 (06)
1A3 (08)
Discrete
Inputs
1Y0 (18)
1Y1 (16)
1Y2 (14)
1Y3 (12)
U7
2Y0 (03)
2y1 (05)
2Y2 (07)
2Y3 (09)
Discrete
Outputs
/EN 1 (01)
74HC244
RA1 (04)
/EN 2 (19)
2A0 (17)
2A1 (15)
2A2 (13)
2A3 (11)
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
SECRC/RDPT/ELD-2012/xxx
Corporate Research
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
16/46
The PORTD of the microcontroller is also indirectly connected to the dip switches (D-SW1) which
can be used to manually set up the ID for DAQ board. Since PORTD serves the dual purpose of
acquiring the DAQ board ID from the dip switch and operating as a general I/O port, it is desirable
to control the data flow (either input or output) for distinction between dip switches and discrete
signals. This is done through the use of octal buffer driver (U5) and octal bus transceiver (U6).
Figure 4.3 describes the pin connections at PORTD of the microcontroller.
4.3.2 External Communication
DAQ system board has driver ICs for RS232 and RS485 communication standards. These driver
ICs share and utilize the USART port of the PIC16F877A microcontroller and thus only one communication standard can be utilized and programmed at a time. Figure 4.4 shows pin connections at the USART port of the microcontroller. Since RS485 is the multipoint communication
standard, it is used to simultaneously connect more than one DAQ board on the same bus in
DAQ system.
Figure 4.4: Pin connections at USART port
PIC16F877A
T2IN (10) T2OUT (07)
R2OUT (09) R2IN (08)
MAX485
RO (01)
DI (04)
RB4 (41)
RS232
TX / RC6 (27)
RX / RC7 (29)
U4
U5
A (06)
B (07)
RS485
MAX232
/RE (02)
DE (03)
4.3.3 Built-in Sensors
The DAQ system is specifically designed to study the behavior of photovoltaic modules under
various weather conditions, hence it is desirable to measure the power output of these modules.
In order to calculate the power output of each photovoltaic module, the module’s current and
voltage must be measured. This is done with one hall effect sensor LA25[12] and one voltage
divider circuit to measure current and voltage respectively.
LA25 is capable of measuring current up to 25A whereas, the voltage divider circuit is configured
and limited up to 1000 Volts DC, which is the maximum allowed voltage that current PV modules
can handle. Both of the LA25 and the voltage divider circuit give output voltage signals in range
of 0 to 5 volts which are connected to the ADC (U2) at channel 6 and 7 (assuming 0 as first channel) respectively as shown in figure 4.5. The input for high current and voltage measurement of
photovoltaic modules is attached at connector PCON of the DAQ board.
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
SECRC/RDPT/ELD-2012/xxx
Corporate Research
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
17/46
Figure 4.5: Connections at ADC (U2) channels 6 and 7
U2
CH 6 (07)
LA25
LTC1290
(ADC)
CH 7 (08)
Voltage
Divider
4.3.4 In System Programming
the DAQ board is fully compatible with ICSP[1] and it can easily be programmed/reprogrammed
using ICD3[5] provided by Microchip Inc. This was added in order to be able to reprogram the
microcontroller without dismounting it from the PCB. ICD3 is a debugging/programming device
which is connected to the ICSP port of the DAQ board. ICD3 can supply power to DAQ system in case that no external power is available during the reprogramming or the DAQ board is
unmounted from installation place. Figure 4.6 shows ICSP port and its pin connections to the
microcontroller.
Figure 4.6: ICSP port
PIC16F877A
/MCLR (02)
VDD (12/35)
GROUND (13/34)
PGD/RB7 (44)
PGC/RB6 (43)
ICSP port
(RJ11-6P)
(1)
(2)
(3)
(4)
(5)
Bottom
view
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
SECRC/RDPT/ELD-2012/xxx
Corporate Research
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
18/46
4.3.5 Power Supply
The DAQ board has one voltage regulator[13] (U14) which supplies regulated 5 volts to all the
active components of the board. The voltage regulator requires 7.5V - 18V to operate and draws
less than 1A. A power supply with 9 - 18V 2A DC output can be connected to CON-01 or CON-02
port of the DAQ board. For indoor testing of the DAQ board, a variable power supply (model:
Velleman PS 603) is provided by ABB CRC. This power supply can output 0 - 30V 2.5A DC. A
regulated 15V output from this power supply is used for the DAQ boards.
4.3.6 PCB size
As mentioned in requirements subsection 3.1.7, the dimension for PCB of DAQ board is such that
it can fit inside the readily available standard size enclosure. Table 3 lists the suitable enclosure
size for DAQ board.
Table 3: Enclosure size for DAQ board
Dimension
Length
Width
Height
mm
255
180
63
inch
10.0
7.1
2.5
Although, any enclosure with IP rating 67 and provided dimensions can be utilized for safe outdoor use of DAQ board but the one (enclosure) currently being used for the project is shown in
figure 4.7. This enclosure is provided by Fibox, with product id UL PC 200/63 HT [15].
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
Corporate Research
SECRC/RDPT/ELD-2012/xxx
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Figure 4.7: UL PC 200/63 HT with DAQ system board
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Page
19/46
Technical Report
SECRC/RDPT/ELD-2012/xxx
Corporate Research
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
20/46
4.4 Software Overview
The data acquisition (DAQ) system is a smart measurement system which uses several DAQ
boards as slave devices to acquire the measurements of multiple analog and digital signals that
come from various sensors including solar radiation, temperature, wind sensors and other environmental sensors. These measurements are then sent to the supervisory computer (master
device) where the measurements are stored and displayed on the graphical user interface (GUI)
application. The communication between the DAQ boards and the computer is realized via using MODBUS (MB) protocol, on request and response basis over RS-485 serial bus as shown in
figure 4.8.
Figure 4.8: Communication between DAQ boards and Computer
DAQ board ID: 01
MB Request to DAQ board 01
MB Response from DAQ board 01
USB-to-RS485
Adaptor
RS-485 bus
DAQ board ID: 02
ABB Database
Server
INDOOR
OUTDOOR
The software for the DAQ system includes,
1. MODBUS drivers for computer and DAQ boards
2. Programming of the DAQ boards (Firmware) and
3. GUI application for supervisory computer user
4.5 MODBUS (MB) Protocol
A brief description about MB protocol is presented below. The provided information is extracted
from MODBUS Application Protocol Specification[16] document. The detailed information about
MB protocol is freely available at official website of MODBUS organization.
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
Corporate Research
SECRC/RDPT/ELD-2012/xxx
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
21/46
4.5.1 Introduction
MB[16] is an application layer messaging protocol, positioned at level 7 of the OSI model[24], that
provides client/server communication between devices connected on different types of buses or
networks. MODBUS organization is responsible to set standards for MB protocol. This protocol
can be implemented on a variety of devices connected on different types of buses or networks including TCP/IP over ethernet and asynchronous serial transmission over RS-232/RS-485 as presented in figure 4.9.
Figure 4.9: MB Communication Stack
4.5.2 General Description
The MB protocol works on application layer of the OSI model. The MB protocol defines a simple
protocol data unit (PDU) which is independent of the underlying communication layers. The
mapping of MB protocol on specific buses or network can introduce some additional fields on
the application data unit (ADU) as shown in figure 4.10.
Figure 4.10: General MB ADU Frame
An ADU is a packet which holds a set of bytes with the combination of the following blocks,
1. Address information (for slave only)
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
Corporate Research
SECRC/RDPT/ELD-2012/xxx
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
22/46
2. Protocol data unit (PDU)
(a) Function code
(b) Data (includes component address and data values)
3. Error check (CRC)
4.5.3 Communication
The communication between the master and the slave devices is done on request and response
basis. The master device builds the ADU and sends it to the slave device via the communication
bus. ADU contains the address of the slave, PDU and CRC code (the calculated check-sum of
all the bytes within MB message). The PDU contains function code and data as shown in figure
4.11. The function code is an one-byte command which tells the slave device to take the appropriate action. The data is the detailed supporting information which includes the address of the
location (on the slave) where a read/write operation is to be performed and the data bytes.
Figure 4.11: Function code and Data block relation
The function code and the data blocks are also the part of the MB standard. The number of
function codes that are supported by the slave device is the choice of the hardware vendor of that
device. Valid function codes are in the range of 1...255 decimal. The function code “0” is not a
valid code. Also, the range 128-255 is reserved and is used for exception responses.
4.5.4 Request and Response
The MB protocol bounds slave/server (DAQ board) devices to communicate in timely manner
with master/client (computer) device and the transaction must be completed in a specified duration (normally 1sec) which is set by the master computer. Failing to keep the time will be a
failure of response also. The client and server communication takes place in a very simple way
in 3 steps. At first, the client initiates a request (1) which is then processed by the server (2). The
server responds to the client accordingly (3). If the client has made a valid request then this transaction will execute without errors. Otherwise the server will respond with a exception code. The
figure 4.12 shows an transaction without errors.
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
Corporate Research
SECRC/RDPT/ELD-2012/xxx
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
23/46
Figure 4.12: MB transaction without errors
In case of an invalid request, the server returns exception code which is equivalent to the original
function code from the request PDU. Moreover function code’s most significant bit is set to logic1 as shown in the figure 4.13. A time-out management is also desirable in order not to indefinitely
wait for an answer which will perhaps never arrive.
Figure 4.13: MB transaction with errors
4.5.5 PDU Structure
The MB PDU size is limited by the size constraint inherited from the first MB implementation on
Serial Line network (max. RS-485 ADU = 256 bytes). Therefore:
P DU = 256 − Ser ver ad d r ess (1 b y t e) − C RC (2 b y t es) = 253 b y t es
The MB protocol defines three types of PDUs[16] which are used by master and slave, that can be
listed as
1. MB Request PDU, mb_req_pdu (initialized by master only)
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
SECRC/RDPT/ELD-2012/xxx
Corporate Research
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
24/46
2. MB Response PDU, mb_res_pdu (initialized by slave only)
3. MB Exception Response PDU, mb_except_rsp_pdu (initialized by slave only)
The mb_req_pdu is defined as:
mb_req_pdu = {function_code + request_data} where
function_code = [1 byte] MB function code
request_data = [n bytes] This field is function code dependent.
The mb_rsp_pdu is defined as:
mb_rsp_pdu = {function_code + response_data} where
function_code = [1 byte] MB function code
response_data = [n bytes] This field is function code dependent.
The mb_excep_rsp_pdu is defined as:
mb_excep_rsp_pdu = {exception_function_code + exception_code} where
exception_function_code = [1 byte] MB function code + 0x80
exception_code = [1 byte] Exception Code[16] depending on the type of error.
4.5.6 Data Encoding
MB uses a ’big-Endian’ representation of addresses and data items. This means that when a
numerical quantity larger then a single byte is transmitted, the most significant byte is sent first.
For example
Reg i st er si ze v al ue
16 bi t s
0×1234
t he f i r st b y t e sent i s 0 × 12 t hen 0 × 34
4.5.7 MB Data Model
MB has four primary tables which make the bases and forms the structure of its data model.
These tables have distinguishing characteristics as listed in table 4.
Primary tables
Table 4: MB Data Model
Object type
Access
Discrete Input
Coils
Input Registers
Holding Registers
Single bit
Single bit
16-bit word
16-bit word
Read-Only
Read-Write
Read-Only
Read-Write
Description
Data can not be altered by application
Data is alterable by application
Data can not be altered by application
Data is alterable by application
The distinction between inputs and outputs, and between bit-addressable and word-addressable
data items do not imply any application behavior. It is perfectly acceptable and very common to
regard all the four tables as overlaying one another.
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
Corporate Research
SECRC/RDPT/ELD-2012/xxx
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
25/46
4.5.8 Function codes
The function code is the main part inside a PDU which specifies the type of request. There are
three categories of MB function codes which are Public, User-defined and Reserved function
codes as shown in figure 4.14.
Figure 4.14: MB Function Code Categories
127
PUBLIC function codes
110
100
User Defined function codes
PUBLIC function codes
72
65
User Defined function codes
PUBLIC function codes
1
The Public function codes are well defined function codes and guaranteed to be unique since
these are validated by MODBUS-IDA.org community.
The User-defined function codes are customizable codes which are not supported by MODBUSIDA.org community. Any user can select and implement a function code that is not supported by
the specification.
The Reserved function codes are used by some companies for legacy products and that are not
available for public use.
Table 5 shows the public function codes which are currently supported by the DAQ board.
Table 5: Public Function Codes Definition
Size
Bit access
16 bits access
Table
Physical Discrete Inputs
Internal Bits
Or
Physical coils
Physical Input Registers
Internal Registers
Or
Physical Output
Registers
Function
Read Discrete Inputs
Read Coils
Write Single Coil
Write Multiple coils
Read Input Register
Read Holding Registers
Write Single Register
Write Multiple Registers
Read/Write Multiple Registers
Code
02
01
05
15
04
03
06
16
23
(Hex)
02
01
05
0F
04
03
06
10
17
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
SECRC/RDPT/ELD-2012/xxx
Corporate Research
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
26/46
4.5.9 Further Reading
A detailed documentation about MB protocol[16] is freely available at official website of MODBUS organization. The documentation also explains the function codes for diagnostics along
with reading or writing the primary tables.
4.6 Firmware
The programming of the DAQ board is mainly focused on the implementation of the MB protocol
in RTU (Remote Terminal Unit) mode. Thus, the DAQ board operates as a slave/server device
and it responds to the requests sent by the master/client device (supervisory computer). The
firmware does not only enable MB communication but it also maps the MB data model (section
4.5.7) over the inputs and outputs of the DAQ board. In this way, all the active components on the
DAQ board can directly be accessed through any MB application software running on the master
computer.
4.6.1 Slave ID
Every DAQ board that is connected to a RS-485 serial bus must have an unique address which is
also called as slave/server ID. The slave ID is set through a package of 8 dip switches (figure 4.15)
available on the board. These dip switches represent one byte (1 byte = 8 bits) in binary format
from left (LSB) to right (MSB) order. Thus, the slave ID in a range of 1 to 255 can be assigned to
the DAQ boards. Every time when the DAQ board is powered on or restarted, it acquires the slave
ID from dip switches. The DAQ board treats dip switches as bits (of single byte) and places 1s
or 0s according to the ON or OFF state of the respective 8 dip switches forming 1 byte value as
shown in figure 4.15.
Figure 4.15: DIP Switches for Slave ID
DIP Switch no. 1 2 3 4 5 6 7 8
ON = 1
OFF = 0
ON
OFF
Now showing:
1000 0000 (Bin) =
0x01 (Hex) or 01 (Dec)
(LSB) BIT: 0 1 2 …..……… 7 (MSB)
4.6.2 I/O Components Mapping
As discussed, the MB data model (subsection 4.5.7) has four primary tables which can be directly
mapped to physical I/O components (i.e. ADCs, DAC, Opto-couplers and Relays) of the DAQ
board. These I/O components interact with external devices like sensors and actuators . Thus,
it is important to gain access of the I/O components on the DAQ board as defined by the MB
protocol. The DAQ board has its I/O components mapped as listed in table 6. The components
and connectors in table 6 represent the (real) labels on the PCB (figure A.3) of the DAQ board.
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
SECRC/RDPT/ELD-2012/xxx
Corporate Research
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
27/46
Table 6: I/O Components Mapping as MB Data Model
Table
Discrete Inputs
Quantity
4
Mapped to
Opto-couplers
Components
Connectors
OPTC1, OPTC2,
OPTC3 and OPTC4
CON-05, CON-06,
CON-07 and CON-08
Coils
4
Relays
SNR-01, SNR-02,
SNR-03 and SNR-04
RELAY-CON1,
RELAY-CON2,
RELAY-CON3 and
RELAY-CON4
Input Registers
16
ADC
U2 and U3
INPUT-CON-01,
INPUT-CON-02 and
INPUT-CON-03
Holding Registers
2
DAC
U9
CON-03
4.6.3 Data Allocation and Addressing
All the physical I/O components of the DAQ board are mapped to some fixed memory locations
(within the PIC16F877A microcontroller) in the form of arrays. Whenever a MB request is received, new data is acquired from or sent to the I/O components. This new data is allocated to
the respective memory locations as listed in table 7 replaces the previous data. Furthermore,
the DAQ board maintains the acquired data in the memory locations and allows to read or write
(if not read only, see MB data model table 4) these memory locations through MB protocol as
shown in figure 4.16. In this way, accessing a memory location is the same as accessing the I/O
component itself.
Figure 4.16: Data Allocation
External Data is
allocated in
Memory (Arrays)
Sensors
Locations
Memory (Arrays)
READ / WRITE
MB Protocol
Accessible
Memory Locations
PV Modules
Any memory location when combined with the slave ID and function code (listed in table 5),
forms an unique address that can be used from the master computer (as illustrated in subsection
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
Corporate Research
SECRC/RDPT/ELD-2012/xxx
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
28/46
4.8). The addresses of the memory locations that are assigned to the I/O components of the DAQ
board are listed in table 7 under the address column.
Table 7: The memory locations on DAQ board
Array Name
Discrete Inputs
(Read only)
Coils
(Read/Write)
Input Registers
(Read only)
Holding Registers
(Read/Write)
Address
00
01
02
03
00
01
02
03
00
01
02
03
04
05
06
07
08
09
10
11
12
13
14
15
00
01
Component
Connection
OPTC1
OPTC2
OPTC3
OPTC4
CON-05
CON-06
CON-07
CON-08
SNR-01
SNR-02
SNR-03
SNR-04
RELAY-CON1
RELAY-CON2
RELAY-CON3
RELAY-CON4
U2(CH0)
U2(CH1)
U2(CH2)
U2(CH3)
U2(CH4)
U2(CH5)
U2(CH6)
U2(CH7)
U3(CH0)
U3(CH1)
U3(CH2)
U3(CH3)
U3(CH4)
U3(CH5)
U3(CH6)
U3(CH7)
INPUT-CON-01(1)
INPUT-CON-01(2)
INPUT-CON-01(3)
INPUT-CON-01(4)
CON_04(PT100)
CON_04(PT100)
PCON(I i n )
PCON(Vi n )
INPUT-CON-02(1)
INPUT-CON-02(2)
INPUT-CON-02(3)
INPUT-CON-02(4)
INPUT-CON-03(5)
INPUT-CON-03(6)
INPUT-CON-03(7)
INPUT-CON-03(8)
U9(CH_A)
U9(CH_B)
CON-03(A)
CON-03(B)
The memory locations mapped to the I/O components is the choice of the programmer of the
DAQ boards and thus the memory locations on the identical DAQ boards may or may not refer
to the same location on all the DAQ boards. This is valid as long as
• the slave ID of each DAQ board is unique on the serial communication bus and
• the user of the master computer possesses proper memory location tables of all the connected DAQ boards.
4.6.4 Flow Diagram
The overall working of the DAQ board is simple. The DAQ board answers the requests sent by the
master computer but only the valid requests are processed by the board. Otherwise an exception
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
SECRC/RDPT/ELD-2012/xxx
Corporate Research
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
29/46
code[16] is sent back to the master computer, that helps the user of the master computer to diagnose the problem with unprocessed requests. Figure 4.17 shows the flow diagram of the DAQ
board’s firmware.
Figure 4.17: Flow Diagram of DAQ board
Start
Initialize I/O
Initialize ADC
Acquire Slave ID
Initialize DAC
Initialize MB1 protocol
Initialize RS485
Initialization
Wait for Request
Obtain
Request
Data
Validate CRC2
Process the Request
Validate Slave ID
Validate Function Code
Is this a
Valid Request?
YES
NO
continue
YES
Perform Data
Read/Write
Is this a
Valid
Slave ID?
NO
Obtain
Exception
code
Ignore the Request
Initiate Response
Send back Response
4.6.5 Serial Port (RS-485) Configuration
The DAQ board is programmed with some fixed configurations for RS-485 serial communication as listed in table 8. These configurations should also be the same for the serial port on the
computer, in order to properly communicate with the DAQ board.
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
SECRC/RDPT/ELD-2012/xxx
Corporate Research
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
30/46
Table 8: Serial Port Configuration
Properties
Baud rate
Data bits
Parity
Stop bits
Flow control
Values
115200
8
None
1
None
4.6.6 Source Code Files
The source code of the firmware is attached in appendix B.1 of the report. The source code is
mainly comprised on two C formatted files as,
1. “main.c”, this is the main source code file which produces the firmware after compilation.
2. “modbus_drivers.c”, this is the library file which defines the routines for the modbus protocol. This file should be placed along with the main code file. The absence of this file would
result in compiling errors.
All the other libraries (C formatted routines files) which are included in the main source code file,
are the part of CCS[17] compiler.
4.6.7 Programming Tools
The firmware for the DAQ board has been written in C language using MPLAB IDE v8.66[18] as
shown in figure 4.18. A demo version of a third party C compiler (CCS Compiler Demo[17]) was
linked to MPLAB in order to compile the C code. However, CCS Compiler Demo[17] can be used
as a trial version with full functional trial period of 45 days. The reason for selecting the CCS compiler is that it includes full documentation and a variety of built-in C libraries for communication
and mathematical operations, that facilitate the programming process.
After compiling the C code using the previously mentioned tools, an Intel HEX[19] object file
which is a text formatted file with “hex” extension, is generated. This hex file is the firmware for
the DAQ board and is uploaded to the microcontroller (PIC16F877A[4]) of the DAQ board using a
programmer/debugger ICD3[5] provided by Microchip Incorporated. The table 9 presents comprehensive lists of all the tools used for developing the firmware and programming of the DAQ
board.
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
SECRC/RDPT/ELD-2012/xxx
Corporate Research
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
31/46
Figure 4.18: MPLAB IDE v8.66
Table 9: Tools used for the Firmware
Vendor
#
Tools
01
MPLAB IDE v8.66[18]
Micorchip Inc.
02
CCS Compiler Demo[17]
CCS Inc.
03
ICD3[5]
Microchip Inc.
Purpose
An integrated development environment
for writing, compiling and programming
microcontrollers produced by Microchip
Inc. only.
A third party compiler for the
microcontrollers belonging to PIC family
produced by Microchip Inc.
A programmer and debugger for all the
microcontrollers produced by Microchip
Inc. only.
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
Corporate Research
SECRC/RDPT/ELD-2012/xxx
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
32/46
4.7 GUI Application Software
The graphical user interface (GUI) application is a part of the DAQ system software which was developed in MATLAB[20]. This application runs from MATLAB IDE installed on the master computer and interacts with the DAQ boards as illustrated in figure 4.8. The main purpose of this
application is to acquire measurement data that is stored at accessible memory locations of the
DAQ boards by using MB protocol.
4.7.1 GUI General Overview
The GUI application’s window is shown in figure 4.19 which is designed using GUIDE[22]. The
GUIDE is a MATLAB graphical user interface development environment which provides a set of
tools for creating graphical user interfaces (GUIs). These tools simplify the process of designing
and programming GUIs.
Figure 4.19: GUI Application’s Window
The source code of the GUI application is not stand alone and it can only be executed inside
MATLAB IDE.
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
Corporate Research
SECRC/RDPT/ELD-2012/xxx
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
33/46
4.7.2 GUI Application Usage
The GUI application (figure 4.19) is simple and easy to use. It has two input requirements,
1. Connection to the serial port (RS-485 serial bus)
2. Slave ID
There can be more than one serial port on a computer system. Thus, the GUI application’s window displays all the available serial ports under the heading “Serial Port”. It should also be
noted that the DAQ boards communicate using RS-485 serial bus whereas modern computer
systems are not equipped with neither RS-485 nor RS-232 port. For this reason an USB-to-RS485
adaptor[21] is connected to the computer, which allows RS-485 communication of the computer
with the DAQ boards.
The GUI application acquires data from the DAQ boards and displays it under the respective
sections on the GUI window. There are four sections on GUI window as can be seen in figure
4.19,
1. Serial Port section shows all the available serial ports on the computer and gives the possibility to the user to connect to the selected serial port.
2. Timer section is used to input a time interval in seconds between data acquisitions and
start/stop the data acquisition. The time interval is a delay period between every automatic
data acquisition from connected DAQ board. The default value for the time interval is 5
seconds.
3. Control section inputs slave/server ID and acquires the status of discrete inputs and coils
from the connected DAQ board. It also has a subsection Write Coils which can turn ON or
OFF any coil. It should be noted that the term coils correspond to the relays on the DAQ
boards as listed in table 6.
4. Input Registers section displays the acquired measurement data from the ADCs of the DAQ
board. This section also has a check box (Log Data) which enables data logging and generates a text file. Moreover, the name of this text file contains the ID of the slave device
from which data are acquired. For example if the slave ID is 1, then the file name would
be “DAQ_dev_001.txt”). The ADC data is added into the generated text file whenever new
data is acquired.
5. Holding Registers section interacts with the 12-bit DAC of the DAQ board. This section
performs read or write operations on the channels A and B of the DAC[7].
4.7.3 Flow Diagram of GUI Application
The GUI application is an event based software. The GUI application’s window generates events
for every mouse click on it’s interactive components like buttons, combo boxes, check boxes etc.
Once an event is generated, an appropriate action is taken by the GUI application which is based
on the type of the event. All the actions are defined in the application source code. Figure 4.20
shows the flow diagram of the GUI’s events and their actions. It should also be noted that a
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
SECRC/RDPT/ELD-2012/xxx
Corporate Research
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
34/46
single event can be triggered at a time and thus, all the actions related to the respective event are
executed in a sequence which is defined in GUI application’s source code.
Figure 4.20: Flow Diagram of GUI Application
Start
= EVENTS
= ACTIONS
Create GUI Window
Obtain a
Mouse Click
Event
Display Error Message
Connect (Serial port)
NO
Close Window
End
Connection
Established?
YES
Obtain a
Mouse Click
Event
E
NO
A
Acquire Discrete Inputs
B
Acquire Coils Status
C
Acquire Input Registers
Slave ID
Provided?
D
D
YES
Data Logging
Enabled?
Get Status (Control)
A
Start (Timer)
Input Registers
B
Enter Loop
C
C
E
C
E
YES
Write Coils (Control)
ON/OFF Relay
E
Stop (Timer)
Exit Loop
E
Append Data
into the Text file
4.7.4 Source Code Files
The source code of the GUI application is written in MATLAB script format. The source code
includes MB driver files and application source code files which should be placed altogether in a
single folder on the computer. The MB drivers support only those functions (as listed in table 5)
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
Corporate Research
SECRC/RDPT/ELD-2012/xxx
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
35/46
which are supported by DAQ board. The GUI application is dependent on the following files,
1. “GUI_DAQ_system.fig”, this file is created with GUIDE for GUI window.
2. “GUI_DAQ_system.m” main application file which handles all the events of GUI window.
This main file is dependent on the following MATLAB function files,
(a) “mb_driver.m” generates MB formatted messages/requests and returns responses of
the DAQ boards to the application. This file utilizes two MATLAB function files,
i. “crc16_mb.m” generates and appends CRC-16 code to the MB messages and returns encoded message.
ii. “validate_crc.m” verifies consistency of received MB messages and returns true
or false status.
(b) “init_port.m” initializes serial port and returns valid serial port object.
(c) “Images.mat” matrix file containing converted ABB logo images.
The source code for above mentioned MATLAB files is listed in appendix B.2.
4.7.5 Programming Tools
The GUI application for computer has been programmed in MATLAB[20] software. MATLAB is a
programming environment for algorithm development, data analysis, visualization, and numerical computation. The GUI application’s window is designed in GUIDE[22] which is the MATLAB’s
graphical user interface development environment. A detailed documentation on how to use the
GUIDE is available in MATLAB’s help section.
4.8 Example MB Request/Response Messages
MB protocol defines a standard frame structure (ADU, figure 4.10) for request or response messages as discussed in subsection 4.5. The communication between the master computer and
slave DAQ boards within the DAQ system fully complies with this standard. The computer broadcasts MB request messages to all the connected DAQ boards over RS-485 serial bus and then only
concerned DAQ boards reply with MB response messages. Every MB request message is initiated
for a specific DAQ board at a time as illustrated in figure 4.8. Furthermore, a MB request/response
message is sent or received in byte-by-byte order and thus constituting packet of bytes.
4.8.1 Example 1 “Reading Coils”
This example illustrates MB request and response messages to read 4 coils (starting from address
0) of a DAQ board whose slave ID is 1.
mb_req_adu = 01 01 00 00 00 04 3D C9
mb_res_adu = 01 01 01 01 90 48
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
SECRC/RDPT/ELD-2012/xxx
Corporate Research
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
36/46
Table 10: Example 1 (Reading coils)
Request
Field Name
Slave ID
Function code
Starting Address Hi
Starting Address Lo
Quantity of outputs Hi
Quantity of outputs Lo
CRC-16 Hi
CRC-16 Lo
(Hex)
01
01
00
00
00
04
3D
C9
Response
Field Name
(Hex)
Slave ID
01
Function code
01
Byte count
01
Coils Status 3 - 0
01
CRC-16 Hi
90
CRC-16 Lo
48
The status of coils 3 - 0 is shown as the byte value 01 hex which is 0000 0001 binary. The right most
bit (LSB) in binary format represents status of coil 0 of the DAQ board and then each bit right to
left order represents the status of coil 1, 2 and 3 respectively (excluding the four bits in MSB since
the DAQ board possesses only four coils). The response shows that the bit representing coil 0 of
the DAQ board is 1 and thus, this coil is ON.
4.8.2 Example 2 “Reading Input Registers”
This example illustrates MB request and response messages to read 3 (from a total of 16) input
registers (7, 8 and 9) of a DAQ board whose slave ID is 2.
mb_req_adu = 02 04 00 07 00 03 01 F9
mb_res_adu = 02 04 06 00 02 0B 15 09 7C 19 F2
Table 11: Example 2 (Reading Input Registers)
Request
Field Name
Slave ID
Function code
Starting Address Hi
Starting Address Lo
Quantity of Input Reg. Hi
Quantity of Input Reg. Lo
CRC-16 Hi
CRC-16 Lo
(Hex)
02
04
00
07
00
03
01
F9
Response
Field Name
(Hex)
Slave ID
02
Function code
04
Byte count
06
Input Reg. 7 Hi
00
Input Reg. 7 Lo
02
Input Reg. 8 Hi
0B
Input Reg. 8 Lo
15
Input Reg. 9 Hi
09
Input Reg. 9 Lo
7C
CRC-16 Hi
19
CRC-16 Lo
F2
The contents of input registers from 7 to 9 are shown as 6 byte values of 0002, 0B15, 097C hex or 2,
2837, 2428 decimal, respectively. All the register are 16-bit in size and thus, each register showing
2-byte value.
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
Corporate Research
SECRC/RDPT/ELD-2012/xxx
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
37/46
4.8.3 Example 3 “Writing Holding Registers”
This example illustrates MB request and response messages to write in 2 Holding registers (0 and
1) of a DAQ board whose slave ID is 1. It should be noted that holding registers can be read or
written unlike input registers which can be read only.
mb_req_adu = 01 10 00 00 00 02 04 00 C8 0D AC 76 BC
mb_res_adu = 01 10 00 00 00 02 41 C8
Table 12: Example 3 (Writing Holding Registers)
Request
Field Name
Slave ID
Function code
Starting Address Hi
Starting Address Lo
Quantity of Input Reg. Hi
Quantity of Input Reg. Lo
Byte Count
Register Value Hi
Register Value Lo
Register Value Hi
Register Value Lo
CRC-16 Hi
CRC-16 Lo
(Hex)
02
10
00
00
00
02
04
00
C8
0D
AC
76
BC
Response
Field Name
Slave ID
Function code
Starting Address Hi
Starting Address Lo
Quantity of Input Reg. Hi
Quantity of Input Reg. Lo
CRC-16 Hi
CRC-16 Lo
(Hex)
02
04
00
00
00
02
41
C8
The holding registers (0 and 1) of the DAQ board are successfully written with values 00C8 and
0DAC hex or 200 and 3500 decimal, respectively.
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
SECRC/RDPT/ELD-2012/xxx
Corporate Research
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
38/46
5 RESULTS
At this point is should be pointed out that the DAQ system is tested for indoor functionality only.
The final test results for the functionality of the DAQ system can be achieved after installing DAQ
boards on the roof top along with the PV modules, since the DAQ boards are designed for operating outdoor.
5.1 ADC test results
During the programming and testing phase of the DAQ board hardware alone, the 12-bit analogto-digital converter (ADC) on-board chip[6] has been tested indoor and results are quite sufficient in terms of accuracy. These results are listed in table 13. The real values are measured
through a calibrated voltmeter provided by ABB CRC 187A, instrument number A38.
#
Table 13: ADC Test Result
ADC Reading Real Value Difference
01
02
03
04
05
06
07
08
09
10
11
12
0.003V
0.035V
0.281V
0.901V
1.213V
1.678V
2.206V
2.826V
3.249V
3.873V
4.280V
4.935V
0.001V
0.032V
0.284V
0.908V
1.219V
1.686V
2.22V
2.847V
3.271V
3.898V
4.304V
4.967V
-0.002
-0.003
0.003
0.007
0.006
0.008
0.014
0.021
0.022
0.025
0.024
0.032
Error %
-200%
-9.38%
1.06%
0.77%
0.49%
0.47%
0.63%
0.74%
0.67%
0.64%
0.56%
0.64%
The results are acquired from the DAQ board by programming the microcontroller for setting
and reading the output of the 12-bit ADC chip (U3). A voltage signal in the range of 0V to 5V is
provided at channel 0 of the ADC chip for every reading. The error ratio is minimized programmatically by taking the average of 100 samples that are acquired in less than 1 second for each
ADC reading. The results are summarized in the table 13.
5.2 Results with GUI application
So far, the results after indoor testing of the DAQ system with complete software are shown in
figure 5.1, where GUI application shows the response of the DAQ board (whose slave ID is 1).
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
Corporate Research
SECRC/RDPT/ELD-2012/xxx
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
39/46
Figure 5.1: Response from DAQ board
5.3 Data Logging
The GUI application is also capable of logging data into a plain text file from input registers.
These input registers carry data from ADC1 and ADC2 of the DAQ board. Thus, the ADCs data is
saved into the text file (DAQ_dev_001.txt) if Log Data (check box) is checked on the GUI window
(as shown in figure 5.1). A preview of DAQ_dev_001.txt file is shown in figure 5.2.
Figure 5.2: Preview of DAQ_dev_001.txt
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
Corporate Research
SECRC/RDPT/ELD-2012/xxx
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
40/46
5.4 Data Manipulation
All the actions which are carried out by the GUI application, can also be performed from the
MATLAB command window. This may facilitate significantly the processing of the data acquired
from the DAQ boards. For this purpose a global variable with the name daq is created as soon
as the GUI application starts it is a structure type variable that synchronizes with all the data
acquired from DAQ board. Thus, it contains all the data acquired from the DAQ board and can
be processed independently without the need of the GUI. A preview of daq variable in command
window is shown in figure 5.3.
Figure 5.3: MATLAB’s Command Window
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
Corporate Research
SECRC/RDPT/ELD-2012/xxx
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
41/46
6 CONCLUSIONS
The DAQ system was designed, programmed and configured successfully. In addition, it fully
complies with the given hardware and software requirements. All the features of DAQ board are
functional. All the components of DAQ board are mounted normally except PIC16F877A which is
mounted on the bottom side of the PCB. This is due to some misunderstanding which caused an
error in the PCB design while referencing the PLCC-44 datasheet. This error has been removed
from the PCB design (as can be seen in appendix A.2) but it exists in four readily produced PCBs.
Furthermore, the DAQ system uses RS485 communication port (as shown in figure 4.4) to connect more than one DAQ board on the single communication bus that is connected to a master
computer. Concerning the developed software, it should be noted that the firmware for DAQ
boards and GUI application software for the master computer work flawlessly. This enables the
control of each DAQ board with a remote computer using the unique ID number which is set
using dip switches on the DAQ board, as shown in figure 4.15. Finally, a USB-to-RS485 converter
adapter is connected to the computer system in order to enable RS485 communication for the
DAQ system as illustrated in figure 4.8.
7 FUTURE WORK
SMT components are becoming prominent in modern electronic devices due to their small size
and power efficiency. Thus, the use of SMT components on the DAQ board can effectively reduce
the PCB size and power consumption. Moreover, a pair of up to 24-bit ADCs can be used for more
precise reading of analog signals.
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
Corporate Research
SECRC/RDPT/ELD-2012/xxx
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
42/46
8 REFERENCES
[1]
Microchip Technology Incorporated, © 2003, In-Circuit Serial ProgrammingTM (ICSPTM )
Guide, Microchip Technology Incorporated, U.S.A, <Link to Datasheet>.
[2]
MCT Paul & Scherer Mikrocomputertechnik GmbH, 1984, SPI - Serial Peripheral Interface,
Martin Schwerdtfeger, Ranzin, Germany, viewed 13 March 2012, <Link to website>.
[3]
Yasir Karim Qureshi, Zeeshan Ahmed Khan, Fateh Muhammad Bilal, Ammar Ismail, Intissar
Mzalouat, 2011, SECRC/PT/TR-2011/271 - Photovoltaic Monitoring System, ABB AB Corporate Research Center, Sweden.
[4]
Microchip Technology Incorporated, © 2003, PIC16F87xA Data Sheet, Microchip Technology Incorporated, U.S.A, <Link to Datasheet>.
[5]
Microchip Technology Incorporated, © 2008, MPLAB® ICD3 In-Circuit Debugger User’s
Guide, Microchip Technology Incorporated, U.S.A, <Link to Datasheet>.
[6]
Linear Technology Corporation, © 2012, LTC1290 - Single Chip 12-Bit Data Acquisition System, Linear Technology Corporation, Milpitas CA, viewed 22 March 2012, <Link to website>.
[7]
Linear Technology Corporation, © 2012, LTC1446 - Dual 12-Bit Rail-to-Rail Micropower
DACs in SO-8, Linear Technology Corporation, Milpitas CA, viewed 22 March 2012, <Link
to website>.
[8]
Maxim Integrated Products, © 2010, MAXIM +5V-Powered, Multichannel RS-232 Drivers/Receivers, Maxim Integrated Products, U.S.A, <Link to datasheet>.
[9]
Maxim Integrated Products, © 2009, MAXIM - Low-Power, Slew-Rate-Limited RS-485/RS-422
Transceivers, Maxim Integrated Products, U.S.A, <Link to datasheet>.
[10] Tyco Electronics Ltd., © 2010, General Purpose Relays PCB Relays - Schrack, Tyco Electronics
Ltd., Berwyn, <Link to datasheet>.
[11] Fairchild Semiconductors Corporation, © 2005, TIL111M, TIL117M, MOC8100M, Fairchild
Semiconductors Corporation, U.S.A, <Link to datasheet>.
[12] LEM, © 2011 , Current Transducer LA 25-NP, LEM, Switzerland, <Link to datasheet>.
[13] Fairchild Semiconductors Corporation, © 2011, LM78XX/LM78XXA 3-Terminal 1A Positive
Voltage Regulator, Fairchild Semiconductors Corporation, U.S.A, <Link to datasheet>
[14] Linear Technology Corporation, © 2011, LT1027 - Precision 5 Volt Reference, Linear Technology Corporation, Milpitas CA, viewed 22 March 2012, <Link to website>.
[15] Fibox Oy Ab, © 2012, UL MNX UL PC 200/63 HT, Fibox Oy Ab, Finland, <Link to Datasheet>.
[16] Modbus Organization Incorporated, © 2006, MODBUS Application Protocol Specification
ver 1.1, Modbus Organization Incorporated, Hopkinton MA, <Link to Document>.
[17] CCS Incorporated, © 2012, CCS Compiler Demo, CCS Incorporated, Waukesha WI, viewed
07 May 2012, <Link to Download page>.
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
Corporate Research
SECRC/RDPT/ELD-2012/xxx
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
43/46
[18] Microchip Technology Incorporated, © 2003, Development Tools Main Page, Microchip
Technology Incorporated, U.S.A, viewed 07 May 2012, <Link to Website>.
[19] Intel, © 1988, Intel Hexadecimal Object File Format Specification Revision A, Intel, U.S.A,
<Link to Document>.
[20] MathWorks Inc., © 1994 - 2012, MATLAB - The Language of Technical Computing, MathWorks Inc., Natick, Massachusetts, USA, viewed 14 May 2012, <Link to Website>
[21] Advantech Co. Ltd, © 1983 - 2012, ADAM-4561 (1-port Isolated USB to RS-232/422/485 Converter), Advantech Co. Ltd, USA, viewed 14 May 2012, <Link to product page>
[22] MathWorks Inc., © 1994 - 2012, MATLAB GUI, MathWorks Inc., Natick, Massachusetts, USA,
viewed 14 May 2012, <Link to Website>
[23] Ing. Ivo Bauer, © 2002 - 2011, ModLink - Welcome to ModLink, OZM Research, Hrochův
Týnec, Czech Republic, viewed 15 May 2012, <Link to Website>
[24] Wikipedia, © 2012, Wikipedia The free Encyclopedia - OSI model, Wikipedia Foundation,
Inc., viewed 26 May 2012, <Link to Website>
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
Corporate Research
SECRC/RDPT/ELD-2012/xxx
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
44/46
9 ENCLOSURES
Prototype design of DAQ board is shown in figure 9.1. This prototype was designed during the
group project conducted for ARGUS[3] project in 2011. The final design of DAQ board is presented in figure 4.1 which is the result of continuous tests and measurements from previous
project.
Figure 9.1: Prototype of DAQ board
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
Corporate Research
SECRC/RDPT/ELD-2012/xxx
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
45/46
A SCHEMATIC AND PCB OF DAQ BOARD
A.1 Schematic of DAQ Board
A.2 PCB Design
A.3 PCB images of DAQ Board
B SOFTWARE FOR DAQ SYSTEM
B.1 Firmware for Server (Source Code)
B.2 Software for Client (MATLAB files)
Please Note:
The schematic diagrams and software for the DAQ system are subjected to the
confidential information and the sharing of such information publically or
commercially, is prohibited.
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.
Technical Report
Corporate Research
SECRC/RDPT/ELD-2012/xxx
Doc. title
Revision
Upgrade of PV Lab and Implementation of Automatic Measurement System
01
Page
46/46
CHANGE HISTORY
Rev.
Chapter
Description
Date / Dep. /Name
01
All
Initial document
<yy-mm-dd>/ <dep.> /
<name>
REVIEW HISTORY
Rev.
Chapter
Reviewer(s)
Date
01
All
<name> / <dep.>
<yy-mm-dd>
We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.
©2009 ABB Ltd.