Beginner Programming Workshop

November 17, 2007 Hauppauge High School

SPBLI - FIRST

Simona Doboli Assistant Professor Computer Science Department Hosftra University Email: [email protected]

Mark McLeod Advisor Hauppauge Team 358 Northrop Grumman Corp.

[email protected]

Agenda

     FIRST Control System MPLAB Environment C Basics FRC Default Code – Robot Driver Control  Demonstration of Basic OI Controls – Robot Autonomous Control  Demonstration of Dead Reckoning Hands-On

FIRST Control System

solenoid motor

FIRST Control Elements

  Hardware – Robot Controller (RC)   User Processor vs. Master Processor PWM, Relay, Digital I/O, Analog, Misc.

– Operator Interface (OI) – Tether cable / Programming cable – Laptop Programming – C Language – MPLAB/mcc18 (write & compile your program) – IFI_Loader (download to robot controller) – Dashboard (optional) – FIRST Default Code

Robot Controller Architecture

  User Processor – What we download to – Runs our code – Reads the digital/analog I/O directly Master Processor – Controls Disable/Autonomous/Driver modes – Disables OI inputs & most RC outputs – Must hear from User periodically or shuts it down – Master Code Software is updated each year

Robot Controller I/O

Analog Gyroscope Analog Rangefinder Potentiometer Motors Servo Team LEDs Banner Sensor Touch Sensor Pressure Sensor Switch Encoder Limit Switch Digital Relays Solenoid Compressor Camera TTL

Getting Started

    Create/Open an MPLAB Project Edit a File Build/Compile Download

MPLAB IFI_Loader .hex file Dashboard (optional) Operator Interface Robot Controller

C Basics

         Structure (#include, functions) IF, THEN, ELSE WHILE FOR =, !

>=, <=, ==, >, <, != &&, || Operators Prototype declarations

C Basics – Structure Program

#include // C header file – standard library function // prototypes #include “myHeader.h” // User header file – user function prototypes int globalVar = 10; // definition global variable – can be used anywhere // in this file void main(void) { // What your program does int result; // local variable – can be used only in main() function result = max(1, 10); // call function max: 1, 10 – actual parameters } int max(int i, int j) // int i, int j = formal parameters { // a function definition }

C Basics – Data Types

Type char unsigned char int unsigned int Size 8 bits 8 bits 16 bits 16 bits short long 24 bits unsigned short long 24 bits long unsigned long 32 bits 32 bits Min -128 0 -32,768 0 -2^23 0 -2^31 0 Max 127 255 32,767 65, 535 2^23-1 2^24-1 2^31-1 2^32-1

C Basics – A simple program

#include #pragma config WDT = OFF int max(int i, int j); // function declaration void main(void) { int m, n, bigger; m = 10; n = 20; bigger = max(m,n); printf("m= %d, n = %d, bigger = %d”, m, n, bigger); while(1); } //############### // Function definition //############### int max(int i, int j) { int result; if (j > i) result = i; else result = j; return result; }

C Basics – if statement

if (touch == 1 && goStraight = 1; light != 0 ) else goStraight = -1; AND Logic

OR Logic (||) !!! NOTE: if (touch =1) vs. if (touch == 1) ASSIGNMENT CONDITION

C Basics – while loop

while (touch == 0) { leftMotor = 5; rightMotor = 5; read(touch); // need to change touch inside // the loop }

// use { } if more than one statement in a loop

C Basics - Exercise

Write a program that computes the first n numbers in the Fibonnacci series: 0, 1, 1, 2, 3, 5, 8, 13. n is an integer number between 0 and 30.

C Basics - Algorithm

int first = 0, second = 1, third; while (n > 0){ third = first + second; output third first = second; second = third; n --; }

FRC Default Code Flow

User Initialization  Main() – User_Initialization() – Do as long as we’re on   New radio packet (slow loop) – Process_Data_From_Master_uP()  – As long as we’re in auto mode do this Default_Routine()  User_Autonomous_Code() Fast loop stuff NO Radio packet ?

YES Driver Routine NO Auto Mode ?

YES User Autonomous

FRC Default Code

 Files to change – user_routines.c (to add switches & change controls)  Default_Routine()  User_Initialization() – user_routines_fast.c

 User_Autonomous() (to add autonomous movement) – user_routines.h

(to share variables between files)

Input / Output

  OI – Inputs    Joysticks x & y (0-254) Buttons (0 or 1) Unused inputs – Outputs  LEDs – lights or 3-digit readout RC – Outputs    Digital I/O for sensors and devices (0 or 1) PWM for motors (0=reverse, 127=stop, 254=forward) Don’t use 13-16 Relay for on/off, e.g., pneumatics (forward, reverse, stop) – Inputs  Analog for sensors, e.g., potentiometers (0 to 1023) – Both  TTL for devices, e.g., camera or LCD screen

Sample OI Controls

(note: OI switches =0 when off and =1 when on) // 2-Joystick drive pwm01 = p1_y; pwm02 = 255-p2_y; // arm joystick pwm03 = p3_y; // motor controlled by switch pwm03 = 127; if (p1_sw_trig == 1) { pwm03 = 254; } // 1-Joystick drive pwm01 = Limit_Mix(p1_y + p1_x - 127); pwm02 = Limit_Mix(p1_y - p1_x + 127); // Limit_Mix keeps pwm between 0 & 254 Sample uses: • Drive • Control arm • Control turret

Sample OI Input/Output

 Changing the OI LED/digital display // LED display on the OI if (user_display_mode == 0) // OI lights are in use (select switch on OI) { Pwm1_green = 1; Pwm1_red = 1; } else // OI digital display is in use { User_Mode_byte = 123; } Sample uses: • Trim joysticks • Display auto selected • Display backup battery voltage

Sample RC Digital Input

 Switches on the Robot Controller (RC Digital Inputs) (note: RC switches =1 when off and =0 when on) // Autonomous selection if (rc_dig_in01 == 1) { Autonomous_1(); } else { Autonomous_2(); } // Limit Switch on arm pwm03 = p3_y; if ((rc_dig_in01 == 1) && (pwm03 > 127)) { pwm03 = 127; } Sample uses: • Limit switches • Autonomous selection • Field starting position • Pressure sensor

Sample RC Analog Input

 Analog Inputs on the RC (e.g., a potentiometer) // Use of arm position sensor (potentiometer) to limit arm movement int armpot; pwm01 = p3_y; armpot = Get_Analog_Value(rc_ana_in03); // value will be 0-1023 if ( (armpot > 900) && (pwm01 > 127) ) { pwm01 = 127; // Neutral } else if (armpot < 100) && (pwm01 < 127) ) { pwm01 = 127; // Neutral } Sample uses: • Position sensors • Gyroscope • Analog rangefinder

Sample RC Relay Output

 Forward / Reverse / Neutral relay8_fwd = 1; relay8_rev = 0; relay8_fwd = 0; relay8_rev = 1; relay8_fwd = 0; relay8_rev = 0; // Single pneumatic solenoid (valve) relay8_fwd = p1_sw_trig; relay8_rev = 0; // Double pneumatic solenoid (valve) relay8_fwd = p1_sw_trig; relay8_rev = !p1_sw_trig; Sample uses: • Pneumatic valves • Compressor on/off • On/off motors // Turn on Compressor when Pressure Switch on digital input 18 says so relay8_fwd = !rc_dig_in18; relay8_rev = 0;

Robot Autonomous Control

     Must be developed under identical environment as in competition Training the robot must be repeated over & over to get right Develop code using old robots or prototypes Plan on multiple autonomous options Use as few distinct movements as possible

Sample Autonomous

// Drive forward and stop Sample_Auto_1() { static int counter=0; } if (counter<100) { counter++; pwm01 = 200; pwm02 = 54; //motor is reversed } else // Make sure it always stops { pwm01 = 127; pwm02 = 127; } May need function prototype: void Sample_Auto_1(void);

Common Issues

        Syntax and typos Program & Data Space Code Too Slow trying to do too much Joystick trim Embedded math (variable overflow) Infinite or too large loops Variables keep values until you change them Unfortunately, it does exactly what you tell it to do

Hands-On

   Vex Robots Timed Autonomous Sensors for Advanced Students 1. Vex w/encoder, turret, gyro 2. Vex w/camera 3. Vex w/pot controlled arm 4. Vex w/rangefinders (IR, sonic) 5. Vex w/swerve drive 6. Edu w/bumper sensor

References

    Programming Quick Start FIRST RC Reference Guide FIRST OI Reference Guide www.chiefdelphi.com/forums Programming forum

Reference Books

     C For Dummies, Volume One C For Dummies, Volume Two C Programming - A Modern Approach K N King “The C Programming Language” Kernighan & Ritchie “The C Answer Book” - Kernighan & Ritchie

 Presentation slides at:

www.cs.hofstra.edu/~sdoboli

or

Team358.org

 Questions/Help please email us. [email protected]

[email protected]