Delay with timers on stm32F107

[sajeed]

Posted on August 28, 2014 at 11:52

Hi

I am working on STM32F107 evaluation board, There is a need for me to implement a delay in ms using H/W timers with polling method. I looked for other examples but they are not working for me can anyone suggest me how to go about. #stm32f107-timers

[Tesla DeLorean]

Posted on August 28, 2014 at 14:23

You could perhaps use One-Shot mode.

The easiest would perhaps be to put the timer in maximal mode where it free-runs across the 16-bit range. You then read TIMx->CNT and observe it tick for the desired number of time units. Set the prescaler so the timer ticks in 1us units, or whatever is convenient.

void delay(uint16_t ticks)
{
uint16_t start = TIMx->CNT;
do { } while((TIMx->CNT - start) < ticks);
}

[sajeed]

Posted on September 15, 2014 at 12:44

Hi Clive

Thanks for the response.I was into some other project for some time. I tried implementing as you suggested but I feel I am missing something important as the timer doesnt start at all, it get stuck in the loop. Here is my implementation void Timer_Init(void) { /* Time base configuration */ TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure; TIM_TimeBaseStructInit(&TIM_TimeBaseStructure); TIM_TimeBaseStructure.TIM_Prescaler = 0; TIM_TimeBaseStructure.TIM_Period = 65535; TIM_TimeBaseStructure.TIM_ClockDivision = 0; TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; TIM_TimeBaseInit(TIM4, &TIM_TimeBaseStructure); /* Enable counter */ TIM_Cmd(TIM4, ENABLE); }

void delay(uint16_t ms)
{
uint16_t start = TIM4->CNT;
do { } while((TIM4->CNT - start) < ms);
}

and the call /*Initialize the timer for delay operations*/ Timer_Init(); Delay_ms(10); right now it is not for 1 ms but it is not working with this delay. Please suggest what mistake is done here. Thanks and Regards Sajeed

[Tesla DeLorean]

Posted on September 15, 2014 at 14:38

Make sure the TIM4 clock is enabled on the APB/AHB bus as appropriate.

If you have a system with a 72 MHz clock, a Prescaler value of 72-1 will get you to 1 us ticks. You won't get 1 ms ticks as 72000-1 won't fit in 16-bit, you could get 500 us ticks with 36000-1

[sajeed]

Posted on September 16, 2014 at 07:55

Hi Clive

Thanks for pointing out the problem and for the explanation. It worked.Thanks and regardsSajeed