chapter 0: programming basics

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Chapter 0: Programming Chapter 0: Programming BASICsBASICs

Presentation based on:

"Robotics with the Boe-Bot"By Andy LindsayParallax, Inc

7/6/04

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Today’s AgendaToday’s Agenda

Overview of STAMP HardwareBasic ElectronicsBuild an LED circuitProgram the STAMP to flash LEDBuild a Speaker CircuitProgram the STAMP to play musicSkills:

• Breadboarding• Use of variables• Use of Control Structures (DO, IF, FOR)

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BASIC Stamp ModuleBASIC 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 IIBasic Stamp II

Self contained computer• “Micro-controller”

Specialized for “embedded”computing (sensing and controlling things)

• Built in programming languagePicBasic (interpreted)Small programming environment runs on a

PC• Connected with a serial cable

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Parallax Basic Stamp IIParallax Basic Stamp II

PIC processor• (Very) roughly the

computing power on the lunar module (much faster, but much less memory)

• 1 million instructions / secNon-volatile memoryPower regulationSerial interface

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Parallax Basic Stamp IIParallax Basic Stamp II

Input/output pins• 16 total (P0…P15)• This is where the action

is• Each pin can be accept

input or produce outputLogic levels (0 or +5v)Also “tricks” for sensing

and producing values in between

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BASIC Stamp and the Board of EducationBASIC Stamp and the Board of Education

The Board of Education provides a platform for programming and connecting devices to the controller.

BreadboarBreadboardd

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Basic ElectronicsBasic 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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ResistorsResistors

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 LEDThe LED

LED: Light Emitting DiodeDiode: 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 20mAwith a 5V supply.

I = V/R

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LED Circuit SchematicLED Circuit Schematic

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The BreadboardThe Breadboard

Breadboards are used to make connections between devices.

TheseTheseConnectConnect

To To BASICBASICStampStamp

I/OI/OPinsPins

Battery + Battery + VoltageVoltage

+5V+5VGroundGround

(Return to (Return to battery --)battery --)

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Check out this video on Check out this video on Breadboards !Breadboards !

http://www.youtube.com/watch?v=q_Q5s9AhCR0

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Building the CircuitBuilding the Circuit

Use 220 Ohms Use 220 Ohms for a brighter for a brighter

LEDLED(Less resistance (Less resistance = more current)= more current)

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Pictorial or Wiring DiagramPictorial or Wiring Diagram

Remember,Remember,Long LED Long LED wire goes wire goes on bottom on bottom

for this for this circuit!circuit!

470 Ohms 470 Ohms

220 Ohms are 220 Ohms are colored colored

Red-Red-BrownRed-Red-Brown

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Connect Components

Note the direction of the Note the direction of the BASIC Stamp ModuleBASIC Stamp Module

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Hardware and SoftwareHardware 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 ProgramYour First Program

Enter the programShortcuts 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 DiscussionCode 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:DEBUGEND

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Code to Blink LEDsCode to Blink LEDs

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Code DiscussionCode 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 2Challenge : Blink the 2ndnd LED 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 CyclingChallenge : 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/BuzzerNext 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 ProgrammingMusical 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 A. Simple Program

 ' {$STAMP BS2} ' Tell what version Stamp we are

using' {$PBASIC 2.5} ' Using latest version 2.5 software

FREQOUT 2, 500, 3000       'Send a 3000 Hz signal to pin 2 for 500 msec

END                        'End of program.  Turns robot off Activity1)      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-LOOPB. 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 secLOOP 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. ActivityB. Activity

4)      Make the robot repeat your tone pattern from 3)

5)      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 ValuesStoring and Retrieving Values

Variable are used to store valuesVariables 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. VariablesC. 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         ' frq can hold a value 0 to 65535n VAR Byte             ’n can hold a value 0 to 255

frq = 1500 'assign a value of 1500 to frqFREQOUT 2, 500, frq 'now send a tone pitch at value of frq

(1500)

frq = 2000 'change frq to 2000FREQOUT 2, 500, frq 'now send a tone pitch at value of frq

(2000)

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Counting and Controlling Counting and Controlling RepetitionsRepetitionsFOR…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 Continue Lab 0 with Step D on handouthandout