STM32L4 + Timer IT + µs counter

[Ghada Dhibi]

Posted on April 24, 2017 at 17:30

Hi All,

I'm using STM32L486RG microcontroler, And 1Wire EEPROM.

I have to use Timer to compute delays type ( delay for 5 �s to 500 �s).

And I'm asking on How to Re-configure Timer on it's interrupt callBack and restart it.

However, I was successfully able to disable the timer once IT callBack was generated. and I restarted it in my freeRTOS task,

I was able to visualize time from oscilloscope, and it was correct timing.

and now, I have to reduce more and more CPU charge by Restatring It on it's Interruption CallBack.

Below my IRQ handler Algorithm:

void TIM1_UP_TIM16_IRQHandler (void)

{ if(LL_TIM_IsActiveFlag_UPDATE(TIM1) == 1) { /* Clear the update interrupt flag*/ LL_TIM_ClearFlag_UPDATE(TIM1); /* Disable the Timer*/ LL_TIM_DisableIT_UPDATE(TIM1);

/* Reconfigure the Timer and restart*/

LL_TIM_SetAutoReload(TIM1, XXX); // Another Timer Period (depending on my 1Wire EEPROM state) LL_TIM_EnableIT_UPDATE(TIM1); } }

Using this method, Timing is not correct, and my eeprom is not working correctly.

Can you help me please ?

Best Regards.

#stm32l4 #eeprom #microseconds #1wire #free-rtos #stm32l4-timer #timer-interrupt

[Tesla DeLorean · Accepted solution]

Posted on April 24, 2017 at 17:39

200 KHz is perhaps a rather aggressive interrupt rate.

You should just need to write the TIM1->ARR with the new period, You'd want to preload (immediate), otherwise it will load at the next update.

[S.Ma]

Posted on April 24, 2017 at 18:23

Alternatively, use a free running timer with say 1000 usec period. Then, if you need a delay or precise cascaded delay, use an output compare interrupt. Disabling the capture interrupt does not freeze timer counting time. It gives you 2 strategies:

- you program a delay from now by reading current timer, add the delay and write the compare register.

- you program a delay from the previous output compare timestamp for exact delays between interrupts...

Output compares can be output to gpios, so it could directly generate the right waveform by hw assistance.

[Ghada Dhibi]

Posted on April 25, 2017 at 10:29

Thank you

Turvey.Clive.002

‌,

I wrote in TIM1->ARR Register with the new period, then I restarted it,

It seems working correctly,

Thank you very much