Change timer period without re initialize it STM32

Question

I'm currently using a timer on my STM32F091VB as below

void MX_TIM3_Init(void)
{
  htim3.Instance = TIM3;
  htim3.Init.Prescaler = 400;
  htim3.Init.Period = 1000;
  HAL_TIM_PWM_Start(&htim3, TIM_CHANNEL_1);
}

...

__HAL_TIM_SET_COMPARE(&htim3, TIM_CHANNEL_1, 1000);

Is there a way to change the htim3.Init.Period on runtime?

I'm using IAR 9.20 as IDE for instance

Answer 1

You can change reload value while the timer is running. You can set it manually via TIM3->ARR = new_value;, where ARR stands for "auto reload register".

You should check reference manual of your MCU - Timer section - to see how many bits wide ARR is, it can be different for different timers. Also, in control register 1 (CR1) there is ARR preload buffer function. If it is enabled, it basically means "don't update ARR with newly written value until the next counter reload". So it will finish the current cycle and only after that change the ARR. If it's disabled, it can change ARR immediately whatever current value of the counter is.

Remember, that timer clock source is not the system clock, typically APBx, possibly with multiplier (2xAPBx is common in most APB clock configurations, it's messy). That is covered in RCC section of the reference manual.