I'm trying to control a TowerPro SG90 servo from my ez430-rf2500 board. I'm able to configure the Timers for PWM operation but there's absolutely no response from the servo. Just a small jerk at start and nothing.
As far as the connections are concerned, I've connected the grounds of ez430, servo and separate USB power supply for the servo to a common point. The pin 2.2 of the MCU is connected to the signal wire of the servo. The servo is powered by a USB power supply as mentioned earlier. Here's my code:-
#include "msp430f2274.h"
#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
P2DIR |= BIT2; // P2.2 = output
P2SEL |= BIT2; // P2.2 = 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);
}
}
}
Could someone tell me what I'm missing here?
