timer_a_ex2_singlePWM.c

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/*******************************************************************************
 * MSP430i2xx Timer_A - Single PWM
 *
 * Description: In this example, the 16 bit Timer_A is configured to output a
 * 75% duty cycle PWM on P1.5. The timer uses SMCLK / 4 for a clock source and
 * outputs a PWM signal with a 8ms period. The PWM generation does not require
 * any interrupts and stays in LPM0. Calculations for the period and duty
 * cycle can be seen below.
 *
 *                MSP430i2041
 *             ------------------
 *         /|\|                  |
 *          | |                  |
 *          --|RST           P1.5|--->75% Duty Cycle PWM
 *            |                  |
 *            |                  |
 *            |                  |
 *
 *
 * Author: Zack Lalanne
 ******************************************************************************/
#include "driverlib.h"
 
// 8ms Period Calculation:
// SMCLK = DCO = 16.384 MHz
// TACLK = SMCLK / 4 = 4.096 MHz
// 8ms / (1 / 4.096MHz) = 32768
#define TIMER_PERIOD        32768
 
// 75% Duty Cycle Calculation:
// TIMER_PERIOD * 0.75 = 24576
#define TIMER_DUTY_CYCLE    24576
 
int main(void) {
 
    Timer_A_outputPWMParam outputPWMConfig = {
        TIMER_A_CLOCKSOURCE_SMCLK,          // SMCLK Clock Source
        TIMER_A_CLOCKSOURCE_DIVIDER_4,      // SMCLK/4 = 4.096 MHz
        TIMER_PERIOD,                       // 8ms
        TIMER_A_CAPTURECOMPARE_REGISTER_1,  // Output on TA0.1
        TIMER_A_OUTPUTMODE_RESET_SET,       // Generate PWM
        TIMER_DUTY_CYCLE                    // 75% Duty Cycle
    };
 
    WDT_hold(WDT_BASE);
 
    // Setting the DCO to use the internal resistor. DCO will be at 16.384MHz
    // SMCLK = DCO = 16.384MHz
    CS_setupDCO(CS_INTERNAL_RESISTOR);
    CS_initClockSignal(CS_SMCLK, CS_CLOCK_DIVIDER_1);
 
    // Setting up P1.5 as TA0.1 for PWM signal generation
    GPIO_setAsPeripheralModuleFunctionOutputPin(GPIO_PORT_P1,
                                                GPIO_PIN5,
                                                GPIO_SECONDARY_MODULE_FUNCTION);
 
    // Configure the timer to use ACLK and interrupt on overflow
    Timer_A_outputPWM(TIMER_A0_BASE, &outputPWMConfig);
 
    // Go into LPM0 with interrupts enabled
    __bis_SR_register(LPM0_bits);
}