CODEWITHSUNDEEP
timerarmdelaystm32cortex-m
Muhammad Fouad Alharoon
Muhammad Fouad Alharoon

Reputation: 77

Implementing a delay using timers in STM32

Simply, I want to implement a delay function using stm32 timers, like the one in AVR microcontrollers "Normal mode". Can anybody help ? I just can't find that in the stm32 datasheet! It only supports PWM, input capture, output compare and one-pulse mode output! N.B: I forgot to mention that I'm using stm32F401 microcontroller

Upvotes: 0

Views: 7313

Answers (2)

user50619
user50619

Reputation: 353

If you want to be able to delay by periods shorter than milli-seconds you can set up a timer to auto-reload and use the internal clock. The internal clock frequency set to the timer is shown in the cube MX clock tab. On my NUCLEO-F446RE most timers get 84MHz or 42MHz.

Timer 3 gets 42 MHz by default. So if I set the pre scaler to 42 and the count period to maximum (0xFFFF if 16 bit) I will have a cycling clock that changes every micro-second.

I can then, using a property of twos complement maths, simply subtract the old time from the new to get the period.

void wait_us (int16_t delay) {
    int16_t t1= htim3.Instance->CNT;

    while (( htim3.Instance->CNT - t1 ) < delay) {
        asm ("\t nop"); 
    }
}

This is an old trick from PIC18 C coding

Upvotes: 0

0___________
0___________

Reputation: 67855

You have very special timer for this purpose called SysTick. Set it to overflow every 1ms. In its handler

static volatile uint32_t counter;

void SysTick_Handler(void)
{
    counter++;
}

inline uint32_t __attribute__((always_inline)) GetCounter(void)
{
    return counter;
}

void Dealy(uint32_t ms)
{
  uint32_t tickstart = GetCounter();

  while((GetCounter() - tickstart) < ms);
}

Upvotes: 3

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