STM8S TIM4 Periodic Timer

What is it?

It is a programmable interval timer implementation for STM8S using TIM4 as an interrupt source.

Why the implementation is so specific? No hardware abstraction?

The whole project is the hardware abstraction for STM8S. I could create the same thing for AVR, MCS-51, etc. And each of them will be easily interchanged based on an underlying CPU.

This library promotes composablity over genericity.

Why TIM4?

TIM4 is the least powerful timer of STM8 that fits the bill. I could create a similar project using another timer if a situation arises. But, for now, TIM4 should be good for most of the cases.

Source code dependencies

• STM8S header

How to use this?

Just include the header to your project.

#include "tim4_periodic_timer.h"

Declaring what to do when the timer tick.

// For example toggle pin B5
uint8_t count = 0;
void ms_handler() {
  count++;
  if (count)
    return;
  ChgBit(GPIOB->ODR, 5);
}

And setup the timer

CONST Tim4PeriodicTimer_Config ms_timer_config = {
    // tick every 1 ms if the CPU runs at 2MHz
    .prescaler = TIM4_PRESCALER_16,
    .reload_value = (0x100 - 125),
    // point to the function we declared earlier
    .ticked = &ms_handler,
};

int main() {
  // most of the functions here has been defined in "stm8s.h"
  // (in STM8S header library)
  disableInterrupts();
  SetBit(GPIOB->DDR, 5);
  SetBit(GPIOB->ODR, 5);
  tim4_periodic_timer__setup(&ms_timer_config);
  enableInterrupts();
  for (;;) {
    wfi();
  }
}

Build recommendations

The opinionated way to build this library is by using the Universal STM8 Builder. You can have it your way if you are also opinionated yourself.

License

STM8S TIM4 Periodic Timer is released under the BSD 3-Clause License. 🎉