Microcontrollers
• What is a Microcontroller
• Characteristics
• Basic Stamp 2 – the controller in the Boe Bot
• Setting up
• Developmental Software
• Hardware
• Sample First Programs
• ASCII
• DEBUG using ASCII
What is a Microcontroller
• Characteristics
• How many microcontrollers did you use today?
What else??
______________
______________
• They are embedded in many common
devices we use every day
• Some other examples:
• Handheld games
• Digital watches
• ????????????????????
• How do microcontrollers differ from PC μProcessors
• μProcessors use external circuitry to interface to non-computer
devices (aka, Input/Output – I/O devices)
What is a Microcontroller
• Characteristics
• How do microcontrollers differ from PC μProcessors (μP)
• Microcontrollers have circuitry to interface and control noncomputer devices
• The heart of both is a small computer on a chip
• Major Components
• Every system based upon a μP or microcontroller contains at
least:
• Arithmetic Logic Unit (ALU) –On Microcontroller
• Memory Unit- Some or all on the Microcontroller
• Control Unit –On Microcontroller
• Input Unit –On Microcontroller
• Output Unit –On Microcontroller
Micro Controller Focused View of a
Typical System Block Diagram
What is a Microcontroller
• Characteristics
• Major Components
• Interconnection of these is shown on the previous slide
• Arrows indicate direction of data, info, and control signal flow
• Large arrows indicate data or information flow
• Smaller arrows indicate the flow of control signals
• Logic Unit (ALU) –On Microcontroller
• Area of the machine that performs
• Arithmetic operations and logical operations
• Memory Unit
• The memory stores information in groups called bytes
• The stored bytes can contain instructions (program) of the µC or
data
• Input Unit
• Consists of all the devices that collect/take eternal information for
input to the system
What is a Microcontroller
• Characteristics
• Major Components
• Shares pins with Output
• Output Unit
• Consists of all the devices that are used to transfer information
from the system to the “outside”
• Shares pins with Input
• Basic Stamp 2 – the controller module in this class
• First Basic Stamp module was introduced in 1992
• Over 3 million sold
• The Stamp 2 is a later model than the on introduced in 1992
• Basic Module components
• Micro controller chip (PIC16C57 on Basic Stamp 2)
• Internal memory (RAM and EEPROM)
What is a Microcontroller
• Basic Stamp 2
• Basic Module
components
• 5 volt regulator
• TTL levels
• 0 – 5V
• Set of basic commands
• Math
• I/O port control
• Programming
• Simplified custom
version of BASIC –
PBASIC
• Speed
• 4000 PBASIC
instructions per second
What is a Microcontroller
• Basic Stamp 2
• Pin-outs
• Pins 1 -24
• Critical
Items
• Sink/
Source limits
on pins 5-20
• VDD on pin
21
• Pin 24 – VIN
limits
• System
ground on
Pin 23
What is a Microcontroller
• Basic Stamp 2
• Embedded Computer Systems
• Modules such as the
BASIC Stamp 2 are
correctly called this
• Sometimes
just “Embedded
System”
• However, they are
most commonly
called microcontrollers
• Carrier Board used
to hold the BASIC
Stamp 2 on the
Boe Bot
Overview of Microcontroller LAB
• Key Aspects
• Software
• Hardware
• Software Setup
• BASIC Stamp Editor
• You will use it on most of the Hand-On parts of the course
• Characteristics
• Aids the writing of PBASIC programs to control the Boe Bot
• Allows simple downloading of these programs to the Boe Bot
• It can them run autonomously
• Also displays messages sent from the Boe Bot
Getting Setup for the Course
• Software Setup
• BASIC Stamp Editor
• Characteristics
• Free from Parallax for use with their products
Desktop Icon
• Should be installed on your computer w/desktop Icon
• Click on it and open it
First Programs
• Overview
• The BASIC Stamp and computer
Communicate over the connecting USB or
Serial cable
• Stream of ones and zeros flow each way
• First Program
• The following program is shown in BASIC Stamp Editor
First Programs
• First Program
• Program continued
• Some lines are typed and some are entered by selecting a button
Clicking on this button will
automatically place '{$STAMP BS2}
at the beginning of your program.
• After entering the program Save it
• Select File then Save
Clicking on this button will automatically
place '{$PBASIC 2.5} at the beginning
of your program.
First Programs
• First Program
• Program continued
• How thee program works
• First 2 lines are comments
• For human reading
• Note the apostrophe
• The net two lines are
comments and Complier directives
• The DEBUG command tells the
Stamp to send the message
• Formatters
• Code word that changes how a Stamp message is displayed
• DEC causes the display of a decimal value
• Control Characters
• CR causes a Carriage return on the line below the characters that
are before it in the message
ASCII
• American Standard Code for Information Interchange
• Most microcontrollers and μPs use this code to represent
each keyboard character and function
• ASCII codes 32 – 126 represent printed characters and symbols
• ASCII codes below 32 correspond to different functions or are
spare
• Some of the functions are:
• cursor up, down, right, left, etc
• space
• Delete
• Etc.
• Machine and human versions of the codes
• Letter “a” ASCII code is 61 in machine readable form 00111101
• Reference page : http://www.asciitable.com/
ASCII
• Bits and Bytes
• Most microcontrollers and μPs smallest unit of memory
used is a Byte
• A Byte consists of 8 bits
• A Bit is the smallest unit of information
• Each bit is either on or off (Logic 1 or 0)
• ASCII only use 7 of the 8 bits in a Byte
• DEBUG using ASCII
• Sample Program
ASCII
• DEBUG using ASCII
• How it works
• Each letter in the DEBUG command corresponds to one ASCII code
symbol that appeared in the Debug Terminal.
DEBUG 66,65,83,73,67,32,83,116,97,109,112,32,50
• 66 is the ASCII code for capital “B”, 65 is the code for capital “A”
and so on. 32 is the code for a space between characters.
• Notice that each code number was separated with a comma.
• The commas allow the one instance of DEBUG to execute each
symbol as a separate command.
• This is much easier to type than 12 separate DEBUG commands.