Stm32 Timer Counter With Registers

Question

I try to use timer1 on STM32f103c8t6 (bluepill). I was read the datasheet and internet response/questions. However I can't understand "how can I adjust period value with registers". I was using timers with HAL library and calculate timing calculations, period and prescaler values etc.

(period)*(prescaler) / (clock Speed) = second

This is my already know formula.

My Clock Speed is 72Mhz and I was adjust Prescaler to 1000. I want to Period value to 72000 and I will have 1 second timer. But I don't know how can ı adjust period value, where is it.

 void TIM1_Config(){
 RCC-> APB2ENR  |= 0x00000400;      //TIM1 CLK Enable
 TIM1-> CR1     |= 0x0083;          //Auto Reload,Update Request Source, Counter Enable
 TIM1-> DIER    |= 0x0003;          //CC1 Interrupt Enable, Update Interrupt Enable
 TIM1-> ARR      = 0x0064;          //100 is set as Auto Reload Value
 TIM1-> PSC     |= 0x03E8;          //1000 is set as Prescaler Value
 TIM1-> (period value I need it)???? // it will set 72000

}

Answer 1

First, be aware that TMR clocks may be different from your system clock. So, be sure that you adjusted APB2 clock correctly.

Assuming that your APB2 clock is also 72 MHz, for 1 second period, you need to divide it by 72000000 (72e6) somehow. You need use ARR & PSC registers such that (ARR + 1) * (PSC + 1) = 72e6 . Keep in mind that these registers are 16-bit, so they can't be greater than 65535.

One possible combination is:

TIM1->PSC = 1124;
TIM1->ARR = 63999;

Please note that I didn't check your code / TMR settings.