Transcript Lec0 - Tom Rebold

Chapter 0: Programming BASICs
Presentation based on:
"Robotics with the Boe-Bot"
By Andy Lindsay
Parallax, Inc
7/6/04
1
MPC ROV Team Forming
 Contact
Jeremy
[email protected]
For more info
Watch their amazing night
dive in Monterey Bay!
http://www.youtube.com/wa
tch?v=lFYAUklUxiQ
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Today’s Agenda
Overview of STAMP Hardware
Basic Electronics
Build an LED circuit
Program the STAMP to flash LED
Build a Speaker Circuit
Program the STAMP to play music
Skills:
• Breadboarding
• Use of variables
• Use of Control Structures (DO, IF, FOR)
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BASIC Stamp Module
A microcontroller, which is like a very small
computer, can be programmed to perform
essential tasks:
•
•
•
•
Monitor sensors to detect the world around it.
Make decisions based on what it senses.
Control motion.
Exchange information with its Roboticist.
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Basic Stamp II
Self contained computer
• “Micro-controller”
Specialized for “embedded”
computing (sensing and controlling things)
• Built in programming language
PicBasic (interpreted)
Small programming environment runs on a PC
• Connected with a serial cable
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Parallax Basic Stamp II
PIC processor
• (Very) roughly the
computing power on the
lunar module (much
faster, but much less
memory)
• 1 million instructions / sec
{
}
Non-volatile memory
Power regulation
Serial interface
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Parallax Basic Stamp II
Input/output pins
• 16 total (P0…P15)
• This is where the action is
• Each pin can be accept
input or produce output
Logic levels (0 or +5v)
Also “tricks” for sensing
and producing values in
between
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BASIC Stamp and the Board of Education
The Board of Education provides a
platform for programming and
connecting devices to the controller.
Breadboard
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Basic Electronics
Voltage (V or E): Potential difference
between 2 points. Volts.
• (+) - A lack of electrons
• (-) – A surplus of electrons
• When a circuit is formed, electrons will flow
to equalize out the 2 sides.
Current (I): The measure of the flow of
electrons. Amps.
Resistance (R): Opposition to current
flow. Ohms.
Ohm's Law: I = V/R
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Resistors
Devices used to insert resistance, or
oppose current flow. Used to limit
current flow.
Color codes are used to indicate the
value.
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From Appendix C
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The LED
LED: Light Emitting Diode
Diode: Device which allows current to
flow in only one direction.
To operate, is must be installed correctly
with respect to polarity.
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A regular LED can be damaged if current
exceed 20mA (milliamps).
Apply ohm's law to find the resistor size
that will limit current to 20mA
with a 5V supply.
I = V/R
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LED Circuit Schematic
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The Breadboard
Breadboards are used to make
connections between devices.
Battery +
Voltage
+5V
These
Connect
To
BASIC
Stamp
I/O
Pins
Ground
(Return to
battery --)
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Check out this video on Breadboards !
 http://www.youtube.com/watch?v=q_Q5s9AhCR0
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Building the Circuit
Use 220 Ohms for
a brighter LED
(Less resistance =
more current)
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Pictorial or Wiring Diagram
470 Ohms 
220 Ohms are
colored
Red-Red-Brown
Remember,
Long LED
wire goes on
bottom for
this circuit!
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Connect Components
Note the direction of the
BASIC Stamp Module
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Hardware and Software
BASIC Stamp, programming board, robot
parts, and various electronic parts are
the hardware.
Software is used to instruct the BASIC
Stamp what to do. Programs are written
on the PC and transferred to and run on
the BASIC Stamp.
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Place the switch (if you have one!) in
programming mode 1 (motors disabled).
Power light on the board will come on.
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Open the software and test
communications.
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Your First Program
Enter the program
Shortcuts for device and language:
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Save your program as
"HelloBoeBot.bs2"
"Run" your program.
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Debug Window appears with message.
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Code Discussion
Comments – used to explain or comment
code – start with apostrophe (')
Directives – such as '{$STAMP BS2} –
used to inform the program of something
special, such as the device being used.
Commands – Word used to instruct the
BASIC Stamp what to do:
DEBUG
END
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Code to Blink LEDs
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Code Discussion
 HIGH defines the pin to be an output and sets it to a HIGH state,
digital 1 or 5V.
• HIGH pin 0-15
• HIGH 13
 LOW defines the pin to be an output and sets it to a LOW state,
digital 0 or 0V.
• LOW pin 0-15
• LOW 13
 PAUSE instructs the BS2 to wait for the defined number of
milliseconds (1/1000 seconds).
• PAUSE time in milliseconds 0-65535
• PAUSE 500
 DO and LOOP instructs the BS2 to repeat the enclosed
statements. More about this will be covered in Programming
Structures.
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Challenge : Blink the 2nd LED
 Modify the program to blink only the second
LED using HIGH and LOW instructions.
 Then Modify to blink both LEDs on and off at
the same time
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Challenge : LED Cycling
 Code a program to perform the following sequence
(use HIGH and LOW):
•
•
•
•
•
•
•
LED1 on P12 ON, LED2 on P13 OFF
Wait 2 seconds
LED1 on P12 ON, LED2 on P13 ON
Wait 1 second
Both LEDs OFF
Wait one-half second
Repeat
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Next Up – The Speaker/Buzzer
A small piezoelectric speaker is included
with your kits.
A frequency can be sounded on it using
the FREQOUT command.
FREQOUT pin, duration, frequency
• pin: Pin it is connected to.
• duration: Length of time in milliseconds.
• frequency: Frequency to play, measured in
Hertz (Hz).
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Add the Piezo speaker circuit to your
breadboard
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Sound the Speaker for 1 second at 1000Hz
freqout 2, 1000, 1000
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Musical And BASIC Programming
We can use freqout to demonstrate
different programming concepts.
You’ll be able to “Hear” what your code
is doing.
Helps to understand logic of your code.
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A. Simple Program
' {$STAMP BS2}
' {$PBASIC 2.5}
FREQOUT 2, 500, 3000
END
' Tell what version Stamp we are using
' Using latest version 2.5 software
'Send a 3000 Hz signal to pin 2 for 500 msec
'End of program. Turns robot off
Activity
1)
make the robot play a 1000 Hertz tone for five seconds.
2)
Make the robot play three notes: 1000, 1500, and 3000 Hertz for
two seconds each. Which one is loudest? Your speaker has a filter
effect.
3)
Change the notes to any other three frequencies you like
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B. DO-LOOP
a structure that repeats code
indefinitely. Change your program for
A to look like this instead:
DO
'Start of loop
FREQOUT 2, 500, 1500
'1500 Hz tone for 0.5 sec
FREQOUT 2, 1000, 3000 ‘ 3000 Hz tone for 1 sec
LOOP
END
'End of program. Turns robot off – unreachable now
TIP: Always indent code that appears in a loop or other control structure
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B. Activity
4)
5)
Make the robot repeat your tone pattern from 3)
Make a folder called Lab0 and Save this as
program sound1.bs2 inside it
6) Now save the program again as sound2.bs2 so we
can make changes to it.
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Storing and Retrieving Values
Variable are used to store values
Variables must be declared prior to being
used. Declaring a variable is giving it a
name, and a size to hold.
VariableName var Size
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C. Variables
name of a place in memory where a number is stored. Delete
all but top 2 lines and add the following:
frq VAR Word
n VAR Byte
' frq can hold a value 0 to 65535
’n can hold a value 0 to 255
frq = 1500
'assign a value of 1500 to frq
FREQOUT 2, 500, frq 'now send a tone pitch at value of frq (1500)
frq = 2000
'change frq to 2000
FREQOUT 2, 500, frq
'now send a tone pitch at value of frq (2000)
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Counting and Controlling Repetitions
FOR…NEXT loops can be used to control
the number of repetitions a segment of
code takes.
FOR StartValue TO EndValue {STEP StepValue}
…
NEXT
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Continue Lab 0 with Step D on handout
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