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The Basics of Programming!

By Christine Luu

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Agenda

What is programming? Overview What you need before you program Familiarizing yourself with MPLAB Programming in C The Code Associating things in the programming with things on the

robot controller and the operator interface Other programming features Back up

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What is programming?

Creating a set of codes to control robot behavior.

The program will take the input from the operator interface (or the sensors, camera) and tell the robot to do what it’s supposed to do.

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What you need before you program Robot Controller & RC Master Code (Processor Firmware) Operator Interface & Joysticks Software

MPLAB IDE v.7.0+ (download from http://www.microchip.com/MPLAB)

IFI Loader v.1.0.10+ (download from www.ifirobotics.com/rc.shtml) MPLAB C18 Compiler (available during build season at

www.usfirst.org) Latest Default Code

Computer with a serial port An assembled, working electronics board Other components (i.e. CMUcam, sensors)

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Overview

Operator Interface

Robot controller

Electronics board

camera

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Familiarizing yourself with MPLAB

Workspace – where you edit your files Build All – compiles your code into

machine language Get to know all the files you will use

Critical files: user_routines.c user_routines_fast.c main.c ifi_aliases.h

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Programming in C

C is a high-level programming language Common commands:

if, else, case, while, loop <=, >=, !=, ==, &&, ||

Syntax: Semicolons – end of any command Comments - /* blahblah */ Brackets { } – used in commands

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Programming in C Variables – a name that you assign to a certain

part of the electronics so you can control its value Example: pwm01 >= 240

Functions a small piece of code that performs a specific task can be called from the main program

Include – tells the program what files to use to control the different components of the hardware Example: #include “ifi_aliases.h”

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Example!if (pwm01>=240){

pwm01=240;}

else if (pwm01<=14){

pwm01=14;}

else{

pwm01=pwm01;}

This piece of code will limit the maximumspeed of the wheels.

Stopped = 127Forward = above 127 up to 255Reverse = below 127 down to 0

So this code is limiting the max forwardspeed of the wheel to 240, and the maxreverse speed to 14. Otherwise, it willmaintain the speed that is given by thejoystick.

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The Code

The Default FRC Code gives you everything you need to get started.

The main files main.c – extremely important, but don’t mess with it. user_routines.c – this is where you modify the code to

make the robot do what you want it to do. user_routines_fast.c – this is where you edit the

autonomous mode (where the robot moves by itself). ifi_aliases.h – defines all the names of the variables

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Associating things in programming w/ things on the robot controllerVariable Variables available of

this typeObject on Board Data Type Poss. Values

pwm## Pwm01-pwm16 Victors (controls motors)

Unsigned char 0-255

relay#_fwd

relay#_rev

Relay1_fwd – relay8_fwd

Relay1_rev – relay8_rev

SPIKE relays Bit 0 or 1

Rc_dig_in## Rc_dig_in01 - rc_dig_in18

Digital sensors Bit 0 or 1

Rc_ana_in## Rc_ana_in01 - rc_ana_in18

Analog sensors 10-bit 0-1024

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Variable Variables available of this type

Object on Board Data Type Poss. Values

Pwn#_red Pwm1_red – pwm2_red

Lights next to “PWM 1” and “PWM 2”

Bit 0 or 1

relay#_red

relay#_green

Relay1_red – relay2_red

Relay1_green – relay8_green

Lights next to “Relay 1” and “Relay 2”

Bit 0 or 1

Switch#_LED Switch1_LED – Switch3_LED

Lights next to “Switch 1-3”

Bit 0 or 1

p#_sw_trig p1_sw_trig – p4_sw_trig

Joystick Trigger Bit 0 or 1

p#_sw_top p1_sw_top

- p4_sw_top

Joystick top button

Bit 0 or 1

p#_wheel p1_wheel – p4_wheel

Joystick Wheel Unsigned char 0-255

p#_y

p#_x

p1_y – p4_y

p1_x – p4_x

X and Y axis of joysticks

Unsigned char 0-255

On Operator Interface

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Other Programming Features

Autonomous CMUcam Sensors

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Things to Keep in Mind

Always make copies of the original code before making any modifications.

Anything you do to the code, no matter how minute it may seem, will have an effect on what the robot does.

Always know the data type you are manipulating (i.e. unsigned char, bit, etc.)

Remember the semicolons! Never download the program to the robot if there

is an error.

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Let’s take a look at last year’s code!

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HELFUL DOCUMENTS Helpful site : http://www.kevin.org/frc/

CMUcam2_workbook.pdfCMUcam2_workbook.zipEverything you need to know about the care and feeding of your nifty CMUcam2 camera sensor is in this document.

CMUcam2_mount_assembly.pdfCMUcam2_mount_assembly.zipCMUcam2 pan and tilt mechanism assembly instructions. This information is also included in the workbook.

CMUcam2_commands.pdf CMUcam2 command dictionary.CMUcam2_data_packets.pdf CMUcam2 data packet documentation.

OV7620_ds.pdfOV7620_ds.zipData sheet for the OV7620 camera module used with the CMUcam2.