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MSP432P401R: Timer32 - Delay function

Michael Dos Santos
Prodigy 30 points

Part Number: MSP432P401R

Hi,

I'm working with a Timer32 to create a simple delay API to use for my future projects.

It seems to work with 1s duration (I don't have an oscilloscope at hand to check for smaller values..).

I would like some advices about the code (Is it enough to work with any ms/µs duration values?), and if a better & easier way to do a delay exists (Maybe with the Timer32 interrupt, or even without a Timer32?).

Remark: the minimum delay duration needed for my future projects is 10µs.

#include "driverlib.h"

void delay_init(void)
{
    Timer32_initModule(TIMER32_0_BASE, TIMER32_PRESCALER_1, TIMER32_32BIT, TIMER32_PERIODIC_MODE);

    Timer32_disableInterrupt(TIMER32_0_BASE);
}

void delay(uint32_t duration_us)
{
    Timer32_haltTimer (TIMER32_0_BASE);
    Timer32_setCount  (TIMER32_0_BASE, 24 * duration_us);
    Timer32_startTimer(TIMER32_0_BASE, true);

    while (Timer32_getValue(TIMER32_0_BASE) > 0);
}

int main(void) 
{
    WDT_A_holdTimer();

    CS_setDCOCenteredFrequency(CS_DCO_FREQUENCY_24);                   // 24000000 Hz
    CS_initClockSignal(CS_MCLK, CS_DCOCLK_SELECT, CS_CLOCK_DIVIDER_1); // 24000000 Hz

    GPIO_setAsOutputPin   (GPIO_PORT_P2, GPIO_PIN0);
    GPIO_setOutputLowOnPin(GPIO_PORT_P2, GPIO_PIN0);

    delay_init();

    while(1)
    {
        delay(1 * 1000 * 1000); // 1s

        GPIO_toggleOutputOnPin(GPIO_PORT_P2, GPIO_PIN0);
    }
}

Thanks,

Michaël

  • 0
    Intellectual 820 points
    For what you're doing/need, at this point, you could perhaps just use the __delay_cycles() intrinsic. no need to waste a timer to do delays , especially not a 32-bit one. see SLAU182 and/or SLAU646.
  • 0 in reply to Jeff Hastings
    Prodigy 30 points

    Hi Jeff,

    Thank you for your answer.

    I thought '__delay_cycles()' wasn't present for the MSP432, but I was wrong.

    It's easy to use, however there're some issues/constraints:
    * An IT executed during the delay increases its duration
    * The duration must be a compile-time constant

    I think I will keep using a Timer32 for the delay() function, the Timer_A are quite enough for my projects.

    -------------------------------------------
    About the code above, maybe using the LowPowerMode + Timer32 with IT could be the best solution, instead of using a polling on the Timer32 value.

    Michaël

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