Beginner Programming Workshop

Beginner Programming Workshop November 17, 2007 Hauppauge High School SPBLI - FIRST Simona Doboli Assistant Professor Computer Science Department Hosftra University Email: Simona.Doboli@hofstra.edu Mark McLeod Advisor Hauppauge Team 358 Northrop Grumman Corp. Mark.McLeod@ngc.com

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

Getting Started • Create/Open an MPLAB Project • Edit a File • Build/Compile • Download

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

C Basics • Structure (#include, functions) • IF, THEN, ELSE • WHILE • FOR • =, ! • >=, <=, ==, >, <, != • &&, || • Operators • Prototype declarations

C Basics – Structure Program #include <stdio.h> // 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

C Basics – A simple program #include <stdio.h> #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 && light != 0 ) goStraight = 1; else goStraight = -1; !!! NOTE: if (touch =1) vs. if (touch == 1) ASSIGNMENT CONDITION AND Logic OR Logic (||)

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() • Default_Routine() • As long as we’re in auto mode do this • User_Autonomous_Code() • Fast loop stuff Radio packet ? NO YES Driver Routine Auto Mode ? NO 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

// 2-Joystick drive pwm01 = p1_y; pwm02 = 255-p2_y; // motor controlled by switch pwm03 = 127; if (p1_sw_trig == 1) { pwm03 = 254; } // arm joystick pwm03 = p3_y; // 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 OI Controls (note: OI switches =0 when off and =1 when on) • 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

// 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 RC Digital Input • Switches on the Robot Controller (RC Digital Inputs) (note: RC switches =1 when off and =0 when on) • 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

// 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; // Turn on Compressor when Pressure Switch on digital input 18 says so relay8_fwd = !rc_dig_in18; relay8_rev = 0; 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; • Sample uses: • Pneumatic valves • Compressor on/off • On/off motors

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 • Vex w/encoder, turret, gyro • Vex w/camera • Vex w/pot controlled arm • Vex w/rangefinders (IR, sonic) • Vex w/swerve drive • 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. Simona.Doboli@hofstra.edu Mark.McLeod@ngc.com

Beginner Programming Workshop