Low Cost DAQ
What is DAQ
Data AcQuisition (DAQ) is the process of measuring an electrical or
physical signals such as voltage, current, temperature, pressure, or sound
with a computer. A DAQ system consists of sensors, DAQ measurement
hardware, and a computer with programmable software. Compared to
traditional measurement systems, PC-based DAQ systems exploit the
processing power, productivity, display, and connectivity capabilities of
industry-standard computers providing a more powerful, flexible, and
cost-effective measurement solution.
DAQ’s Block Diagram
DAQ Device’s Components
Signal Conditioning
Signals from sensors or the outside world can be noisy or too
dangerous to measure directly. Signal conditioning circuitry
manipulates a signal into a form that is suitable for input into
an ADC. This circuitry can include amplification, attenuation,
filtering, and isolation. Some DAQ devices include built-in
signal conditioning designed for measuring specific types of
sensors.
DAQ Device’s Components
Analog-to-Digital Converter (ADC)
Analog signals from sensors must be converted into digital
before they are manipulated by digital equipment such as a
computer. An ADC is a chip that provides a digital
representation of an analog signal at an instant in time. In
practice, analog signals continuously vary over time and an
ADC takes periodic “samples” of the signal at a predefined
rate. These samples are transferred to a computer over a
computer bus where the original signal is reconstructed from
the samples in software.
DAQ Device’s Components
Computer Bus
DAQ devices connect to a computer through a slot or port.
The computer bus serves as the communication interface
between the DAQ device and computer for passing
instructions and measured data. DAQ devices are offered on
the most common computer buses including USB, PCI, PCI
Express, and Ethernet. More recently, DAQ devices have
become available for 802.11 Wi-Fi for wireless
communication. There are many types of buses, and each
offers different advantages for different types of applications.
Market Background
• Nowadays, there is several low cost DAQ
applications, with an average 200$ price tag.
• Typical dimensions varies from a size of a
cigarettes pack.
• Typical power consumption of such devices
varies between : ~ 0.1W - 0.5W
Project Motivation
• Ultra low cost MSP430™ series
Microcontroller – starting from 2$
• Ultra low power consumption ~20uW
• Integrated USB2 controller with PHY
• Small dimension – can be applied on an USB
dongle
Principle of operation
• To implement the DAQ device, we will use an
MSP430F5529’s GPIOs for collecting analog
DATA and to generate a desired output.
Integrated ADC will convert the signals. As a
DAQ’s manipulator and a data analyzer, we
will use a PC powered with NI LabView.
Thanks to the integrated USB2 controller, we
will be able to achieve a 12Mb/s data link.
Introducing the MSP as the heart
of the DAQ
• 16-Bit RISC Architecture, 8+2KB SRAM, up to 25-MHz
System Clock
• An ADC with a 12 bit A/D conversion for collecting
the analog data
• Up to 43 GPIO’s for custom use
• 4 16-bit timers for setting an analog sample rate, and
generating PWM signal.
• Full speed USB with integrated PHY
Introducing the MSP as the heart
of the DAQ
Things to do
• Check what an USB class device is the best for
our application
• Implement an USB client side communication
using a TI MSP430 USB API
• Implement the DAQ’s functions and operation
modes
Things to do
• Implement a Windows driver for
communicating with a MSP430F5529
• Using LabView, implement a GUI for data
acquisition
Development process: Tools
MSP430F5529 USB Experimenter’s Board
Development process: Tools
MSP430F5529 USB EB Features
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USB Based Development Platform
5-pad capacitive touch strip
microSD Card Slot
102x64 grayscale, dot-matrix LCD with
backlight
Development process: Tools
MSP430F5529 USB EB Features
• 4 push buttons
• 3 GP LEDs, 5 LEDs for capacitive touch
buttons, and 1 LED Power indicator.
• Scroll wheel/Potentiometer
• Integrated eZ-FET for Spy-Bi-Wire (2-wire
JTAG) programming and debugging
Development process: Tools
MSP430F5529 USB EB Features
• JTAG header for full 4-wire JTAG programming
and debugging
• Easy access to F5529 I/O pins by 100mil
header
Development process: Tools
TI Code Composer Studio Integrated
Development Environment v5
• CCS is used for MSP430 target code
development and designing. It features
integrated ez-FET driver for MSP430F5529 EB
flasher/debbuger, MSP430 family API, various
debugger tools, and C compiler for MSP430
MCUs.
Development process: Tools
MSP430 USB API Stack for CDC/PHDC/HID/MSC
This API is used for implementing a client side
USB communication with a Host. For our
application, we have chose the CDC USB class.
Classes description, and the choice reason will
be explained later
Development process: Tools
National Instruments LabView
LabVIEW (short for Laboratory Virtual
Instrumentation Engineering Workbench) is a
system design platform and development
environment for a visual programming language
from National Instruments.
Development process: Tools
National Instruments LabView
This design platform was chosen for
implementing the PC host side client
application. The main reason of this choice is
ease and relatively short development time of
the host application
Development process:
Digital I/O
The digital I/O features include:
• Independently programmable individual I/Os
• Any combination of input or output
• Individually configurable P1 and P2 interrupts.
• Independent input and output data registers
• Individually configurable pullup or pulldown resistors
Development process:
Digital I/O
• MSP459F5529 have eight digital I/O ports implemented (P1 to
P8, PU and PJ).
• P1 to P7 ports contain eight I/O lines; however, P8, Port U and
Port J contains three, three and four lines respectively.
• Ports P1 and P2 always have interrupt capability.
Each interrupt for the P1 and P2 I/O lines can be individually
enabled and configured to provide an interrupt on a rising or
falling edge of an input signal.
• Most pins connect to a more specialized peripheral, but if that
peripheral is not needed, the pin may be used for generalpurpose I/O.
Development process:
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Digital I/O
We are going to use the following ports:
P1 or/and P2 - Timers and External interrupts.
P6, P7.0-P7.3 – 12 bit ADC inputs.
P5.0 and P5.1 - ADC reference voltage inputs.
PU – Communication with PC via USB
protocol.
• P5.2-P5.5 – Inputs for 2 crystal oscillators.
Development process:
Digital I/O
For example Port 6 that can be used as GPIO and as
Analog signal inputs for ADC:
Development process: USB
Universal Serial Bus (USB) is an industry standard developed in
the mid-1990s that defines the cables, connectors and
communications protocols used in a bus for connection,
communication and power supply between computers and
electronic devices. This communication protocol is widely
used nowadays for communicating between a host PC and
various detachable peripherals
Development process: USB
MSP430F5529 Block diagram
Development process: USB
MSP430 USB API stack supported USB classes
1. HID
2. MSC
3. CDC
4. PHDC
Development process: USB
HID
• Human interface device class
• Pros: there is no need for a driver for a Host
machine. Great advantage for limited access
workstations
• Contras: 64KB/s
Development process: USB
MSC
• Mass storage Device Class
• Designed for storage operations
• Supports only bulk transfer
Development process: USB
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PHDC
Personal Healthcare Device Class
Certified for use with several Personal
Healthcare devices such as blood pleasure
monitor, thermometer, weight scale and etc.
Pros: Easy development
Contras: For PH devices only, consumes large
amount of RAM
Development process: USB
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CDC
Communication device class
For use with various communication devices.
Simple protocol
Pros: Widely used virtual com class. High
communication speed. Simple host application
development
Contras: At the first use on the host workstation,
an appropriate driver installation is needed.
Disadvantage for a limited access workstations
Development process: USB
DAQ’s USB Class
• For implementing an USB communication with
a host PC, was decided to use the CDC
protocol due to it’s high data rate speed (up to
6.3Mbp/s) and simple communication
protocol that fits our needs
Development process: USB
DAQ’s USB Class
• Relying on the USB API stack, we developed a
target code that gives the ability to the
MSP430F5529 to communicate with a host PC
through virtual COM port.
Development process: USB
DAQ’s USB Class
• USB communication target code is initializing
MSP430 device as CDC class device with a
temporary (development) VID/DID. USB
interrupt register launches several routines to
handle USB events such as initial connection
handshake, data transmit ready, data receive
ready, device disconnected, host busy and
etc…
Development process: USB
MSP430 USB communication code
• USB communication target code is initializing
MSP430 device as CDC class device with a
temporary (development) VID/DID. USB
interrupt register launches several routines to
handle USB events such as initial connection
handshake, data transmit ready, data receive
ready, device disconnected, host busy and
etc…
Development process: USB
USB Input handling
• USB target code designed to continuously
receive all incoming data and to store it in the
buffer. After receiving the CR (Enter) character,
a C case routine handle the received data to
perform the user desired request and the
buffer is cleared.
Development process: USB
USB output
• After the desired DAQ’s operation performed,
MCU will prepare the collected data and
transmit it back to the PC. Yet not designed a
transmitted data package. It is up to the host’s
application to handle and to decode the
package
Development process: ADC
• An analog-to-digital converter (abbreviated
ADC) is a device that converts a continuous
signal to a discrete time digital representation.
• Typically, an ADC is an electronic device that
converts an input analog voltage or current to
a digital number proportional to the
magnitude of the voltage or current.
Development process: ADC
MSP430F5529 ADC Block diagram
Development process: ADC
• The ADC module supports 12-bit analog-todigital conversions. The module implements a
12-bit SAR core, and a 16-word conversionand-control buffer. The conversion-andcontrol buffer allows up to 16 independent
analog-to-digital converter samples to be
converted and stored without any CPU
intervention.
Development process: ADC
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Main features
Greater than 200-ksps maximum conversion rate
Sample-and-hold with programmable sampling
periods controlled by software or timers.
Conversion initiation by software or timers.
Software-selectable on-chip reference voltage
generation (1.5 V, 2.0 V, or 2.5 V)
Software-selectable internal or external reference
Up to 12 individually configurable external input
channels
Development process: ADC
Main features
7. Conversion channels for internal temperature sensor,
AVCC, and external references
8. Independent channel-selectable reference sources for
both positive and negative references
9. Selectable conversion clock source
10. Single-channel, repeat-single-channel, sequence
(autoscan), and repeat-sequence conversion modes
11. Interrupt vector register for fast decoding of 18 ADC
interrupts
12. 16 conversion-result storage registers
Development process: ADC
Used ADC registers
1. ADC12CTL0: For setting a sampling time and turning the ADC
module on
2. ADC12CTL1: For choosing an internal sampling timer, setting
continuous/single sampling mode and choosing a conversion
memory register
3. ADC12MCTLx: Assigning a memory register conversion input
channel
4. ADC12IE: Enabling interrupts corresponding “memory
loaded” flag
5. ADC12IV: Interrupt vector events
Development process: ADC
ADC decoding formula
N A D C  4095 *
• Vin – Analog input
• Vr+ - Positive reference voltage
• Vr- - Negative reference voltage
V in  V R 
VR  VR
Development process:
Timers
MSP430F5529 features 4 16bit Timers
• Timer A0 with 5 Capture/Compare registers
• Timer A1 with 3 Capture/Compare registers
• Timer A2 with 3 Capture/Compare registers
• Timer B0 with 7 Capture/Compare registers
Development process:
Timers
16-bit timer/counter with up to seven
capture/compare registers. Timer can support
multiple capture/compares, PWM outputs, and
interval timing. Timer also has extensive
interrupt capabilities. Interrupts may be
generated from the counter on overflow
conditions and from each of the
capture/compare registers.
Development process:
Timer
Development process:
Timer
We intend to use the timer for a sampling
interval, as well as PWM generator. Timers code
development hasn’t started yet.
Gantt
task name
duration
Reading materials
Reading materials
Experimenting with MSP430F5529
Characterization
1 week
1 week
1 week
1 week
C code writing:
10 weeks
USB Interface
3 weeks
ADC modes library
4 weeks
DAQ’s modes – MSP side
2 weeks
Host PC LabView GUI development 4 weeks
Fine tuning
Mid presentation
Verification and Debugging
Final report
Final presentation
1 week
1 weeks
3 weeks
7 weeks
1 weeks
26/3 2/4 9/4 16/4 23/4 30/4 7/5 14/5 21/5 28/5 4/6 11/6 18/6 25/6
30/7 6/8 13/8 20/8
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References
• Data Aacquisition -http://en.wikipedia.org/wiki/Data_acquisition
• NI Low-Cost DAQ USB 6008 http://sine.ni.com/nips/cds/view/p/lang/en/nid/201986
• TI datasheets:
• http://www.ti.com/tool/msp-exp430f5529
• http://www.ti.com/product/msp430f5529
• http://focus.ti.com/paramsearch/docs/parametricsearch.tsp?family=analog
&familyId=2020&uiTemplateId=NODE_STRY_PGE_T
• http://www.usb.org/home
• http://www.ti.com/tool/msp430usbdevpack
• http://www.ni.com/labview/
• http://www.ni.com/data-acquisition/
• http://www.ni.com/data-acquisition/usb/