servo.c

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#include "main.h"

#define period 20
//we found these by trial and error basically
//( 20ms - 1.5 )* 16,000 = 296000 should be the neutral position at 90 degrees, but we had to calibrate
//calibrated for robot 3
#define clockwise 319488 //319488 -- starting point
#define cclockwise 292096 //292096 -- ending point
#define TIMER4B_PRESCALER 50


volatile int overflow;
volatile int rise_time; // start time of the return pulse
volatile int fall_time;// end time of the return pulse
volatile int j;

volatile float servo_angle;




void timer_init()
{
    unsigned int pulse_period = period * 16000;
    unsigned int match = ((period-1.5)*16000);

    SYSCTL_RCGCTIMER_R |= SYSCTL_RCGCTIMER_R1;
    TIMER1_CTL_R &= ~TIMER_CTL_TBEN; //disable timer1B
    TIMER1_TBMR_R |= 0xA; //set to periodic and PWM
    TIMER1_TBMR_R &= ~0x4; //disable capture mode
    TIMER1_CFG_R |= TIMER_CFG_16_BIT; //set to 16bit
    TIMER1_TBPR_R |= pulse_period>>16; //set timer prescaler
    TIMER1_TBILR_R |= pulse_period & 0xFFFF; //set period
    TIMER1_TBPMR_R |= (match>>16); // set match prescaler
    TIMER1_TBMATCHR_R |= match&0xFFFF; // set timer value for initial intpt
    TIMER1_CTL_R |= TIMER_CTL_TBEN;
}


void clock_timer_init(void)
{
    SYSCTL_RCGCTIMER_R |= SYSCTL_RCGCTIMER_R4; // Turn on clock to TIMER4

    //Configure the timer for input capture mode
    TIMER4_CTL_R &= ~(TIMER_CTL_TBEN); //disable timerB to allow us to change settings
    TIMER4_CFG_R |= TIMER_CFG_16_BIT; //set to 16 bit timer

    TIMER4_TBMR_R |= TIMER_TBMR_TBMR_PERIOD; //set for periodic mode, down count

    TIMER4_TBPR_R |= TIMER4B_PRESCALER - 1;  // 200 ms clock

    TIMER4_TBILR_R = (int)(16000000/(TIMER4B_PRESCALER * 5)); // set the load value for the 0.2 second clock

    //clear TIMER3B interrupt flags
    TIMER4_ICR_R = ( TIMER_ICR_TBTOCINT); //clears TIMER4 time-out interrupt flags
    TIMER4_IMR_R |= ( TIMER_IMR_TBTOIM); //enable TIMER4(A&B) time-out interrupts

    //initialize local interrupts
    //NVIC_EN2_R = 0b11000000;
//  NVIC_ENn_R = 0x????????; //#warning "enable interrupts for TIMER4A and TIMER4B" n = 0, 1, 2, 3, or 4
    //go to page 105 and find the corresponding interrupt numbers for TIMER4 A&B
    //then set those bits in the correct interrupt set EN register (p. 142)

    //IntRegister(INT_TIMER4B, TIMER4B_Handler); //register TIMER4B interrupt handler

    IntMasterEnable(); //intialize global interrupts

    TIMER4_CTL_R |= (TIMER_CTL_TBEN); //Enable TIMER4A & TIMER4B
}


void servo_init(){
    SYSCTL_RCGCGPIO_R|= SYSCTL_RCGCGPIO_R1;
    GPIO_PORTB_PCTL_R |= GPIO_PCTL_PB5_T1CCP1;
    GPIO_PORTB_DEN_R &= ~0x20;
    GPIO_PORTB_DIR_R|= 0x20;
    GPIO_PORTB_AFSEL_R|=0x20;
    GPIO_PORTB_DEN_R |= 0x20;
}


void match_set(int match)
{
    TIMER1_TBMATCHR_R = (match  & 0xFFFF); //set match, 16 LSB's
    TIMER1_TBPMR_R = (match >> 16); //set match, 8 MSB's
}


void servo_setAngle(double degrees)
{
    //cclockwise = 180 degrees and clockwise = 0 degrees
    double slope = (cclockwise- clockwise)/(180.0);

    //set match value
    //slope is the amount the match value will change per degree
    //clockwise is the intercept of the line
    //y = mx+b
    unsigned int match = slope*(degrees) + clockwise;

    match_set(match);
    timer_waitMillis(50);

    servo_angle = degrees;
}