gistfile1.c

#include "msp430g2553.h" // make sure you change the header to suit your particular device.
 
// Connect the servo SIGNAL wire to P1.2 through a 1K resistor.
 
#define MCU_CLOCK           1100000
#define PWM_FREQUENCY       46      // In Hertz, ideally 50Hz.
 
#define SERVO_STEPS         180     // Maximum amount of steps in degrees (180 is common)
#define SERVO_MIN           700     // The minimum duty cycle for this servo
#define SERVO_MAX           3000    // The maximum duty cycle
 
unsigned int PWM_Period     = (MCU_CLOCK / PWM_FREQUENCY);  // PWM Period
unsigned int PWM_Duty       = 0;                            // %
 
void main (void){
 
    unsigned int servo_stepval, servo_stepnow;
    unsigned int servo_lut[ SERVO_STEPS+1 ];
    unsigned int i;
 
    // Calculate the step value and define the current step, defaults to minimum.
    servo_stepval   = ( (SERVO_MAX - SERVO_MIN) / SERVO_STEPS );
    servo_stepnow   = SERVO_MIN;
 
    // Fill up the LUT
    for (i = 0; i < SERVO_STEPS; i++) {
        servo_stepnow += servo_stepval;
        servo_lut[i] = servo_stepnow;
    }
 
    // Setup the PWM, etc.
    WDTCTL  = WDTPW + WDTHOLD;     // Kill watchdog timer
    TACCTL1 = OUTMOD_7;            // TACCR1 reset/set
    TACTL   = TASSEL_2 + MC_1;     // SMCLK, upmode
    TACCR0  = PWM_Period-1;        // PWM Period
    TACCR1  = PWM_Duty;            // TACCR1 PWM Duty Cycle
    P1DIR   |= BIT2;               // P1.2 = output
    P1SEL   |= BIT2;               // P1.2 = TA1 output
 
    // Main loop
    while (1){
 
        // Go to 0°
        TACCR1 = servo_lut[0];
        __delay_cycles(100000);

        // Go to 45°
        TACCR1 = servo_lut[45];
        __delay_cycles(100000);
 
        // Go to 90°
        TACCR1 = servo_lut[90];
        __delay_cycles(100000);
 
        // Go to 180°
        TACCR1 = servo_lut[179];
        __delay_cycles(100000);
 
        // Move forward toward the maximum step value
        for (i = 0; i < SERVO_STEPS; i++) {
            TACCR1 = servo_lut[i];
            __delay_cycles(20000);
        }               
        // Move backward toward the minimum step value
        for (i = SERVO_STEPS; i > 0; i--) {
            TACCR1 = servo_lut[i];
            __delay_cycles(20000);
        }
   }
}