Generate a single pulse of 12ns with stm32u5

[lucascalam]

Hi there.

I’m trying to generate a 12 ns pulse for a time-of-flight (ToF) application.

I’m using an STM32U5 microcontroller, and I’d like to know whether one of the general-purpose timers (TIM2/TIM3/TIM4/TIM5) can produce a pulse that narrow. With a 160 MHz timer clock, the time resolution is about 6 ns, so in principle it seems feasible, but I may be overlooking something.

Thanks!

[Ozone]

I think you will need to get deeper into the reference manual of your MCU.
Most STM32 devices have a dozen or more timers, usually on different peripheral busses, while not all those busses support the same clock frequencies.
In most devices I worked with, the peripheral busses support only a maximum of core-clock/2.
I have no specific knowledge of STM32U5 devices, though.

[lucascalam]

hello @T_Hamdi , the frequency of the clock is set to 160MHz. 

I checked also the value with  LL_RCC_GetSystemClocksFreq().

Additonally, in the measurement I got the following: (see IMG_0794.jpeg).

 which shows that the period between pulse is 1.25us. In the code, I set the period to 200 ticks:

LL_TIM_SetAutoReload(TIM2, 200);

therefore, we can confirm that the frequency is properly set (otherwise, the period would be different not  1.25us).

I have no clue what might be causing this issue.

[LCE]

Looks at least that you're quite close with 62.5 ns (?).

Check the timer registers, compare to ref manual. Is the "compare" register really set to 2 (or does this have the typical +1, wouldn't make sense in this case...) ?

The basic timer functions like this are not to hard to do with direct register settings.

[waclawek.jan]

What's your hardware, a "known-good" board like Nucleo or Disco, or your own?

Do you measure directly at the PA1 pin? What is connected to that pin?

JW

[MM..1]

Preloading with one pulse mode is absurd, and too place in while 

LL_TIM_EnableCounter(TIM2);

[waclawek.jan]

Yes, they all are mistakes, but neither of them should result in cca 10x longer pulse.

JW