STM32F7 - thread sleep of a few microseconds

[elagil]

Hello!

I want to make a polling based one-wire driver because I want to be able to use it on multiple pins without occupying PWM/Timer blocks. Therefore, I need delays in the range of a few microseconds. I tried using

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chThdSleepMicroseconds(n)


in conjunction with

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#define CH_CFG_ST_FREQUENCY                 1000000


so that systick is 1 MHz. So, I should be able to resolve 1 us ticks with some inaccuracy due to

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#define CH_CFG_ST_TIMEDELTA                 2


I now try to toggle a pin and place a 10 microsecond delay between setLine and clearLine operations. The delay between the switching is never below 40 us. Am I missing something here? Why can the delay not be less than this?

The processor runs at 200 MHz.

Thanks in advance,
Adrian

[Giovanni]

Hi,

You have to consider jitter in the system, you cannot have such accurate delays when ISRs take several microseconds.

You may use the "polled" delay functions in both Kernel (chSysPolledDelayX()) and HAL (gptPolledDelay()) but those would still be partially affected by IRQ-caused jitter.

Giovanni

[elagil]

Hello,

the gptPolledDelay works fine for my case, thank you! I get the delays with sufficient accuracy.