The exact frequency of the timer

ghost07
Posts: 36
Joined: Mon Oct 03, 2022 11:47 am

Re: The exact frequency of the timer

Postby ghost07 » Fri Sep 08, 2023 12:57 pm

I see you are facing very similar problem as I do with frequent SPI reads triggered by interrupt.
In my case, I found out that 4 ms delay was caused by xTaskList() or uxTaskGetSystemState() that calls vTaskSuspendAll() in its implementation.
Check if you don't call one of these functions every 5 sec.
Or maybe ESP_LOGx() could have similar effect, try to disable or prolong prints to console and check if the 40 ms delay occurs less frequently.

Alternatively, if you can modify HW, you can try to use some Paralel-in Serial-out shift register and convert it to some form of SPI communication.
MicroController wrote:
Sat Sep 02, 2023 3:34 pm
Fortunately, running an ISR per se doesn't require a context switch between tasks.
How do interrupt execution work then? Do interrupts have its own set of CPU registers, so the current task's registers can stay untouched without any context switch?

MicroController
Posts: 1692
Joined: Mon Oct 17, 2022 7:38 pm
Location: Europe, Germany

Re: The exact frequency of the timer

Postby MicroController » Fri Sep 08, 2023 4:06 pm

ghost07 wrote:
Fri Sep 08, 2023 12:57 pm
MicroController wrote:
Sat Sep 02, 2023 3:34 pm
Fortunately, running an ISR per se doesn't require a context switch between tasks.
How do interrupt execution work then? Do interrupts have its own set of CPU registers, so the current task's registers can stay untouched without any context switch?
You are right in that interrupts and task switches have much in common; the difference is just that, in a "pure" (non-yielding) ISR, FreeRTOS's vTaskSwitchContext isn't invoked to find another runnable/"ready" task before returning.
So, yes, there is a context switch between a running task and an ISR, but an ISR alone doesn't imply switching from one task to another. Fine hair to split :)

mikl604
Posts: 26
Joined: Thu Aug 24, 2023 3:15 pm

Re: The exact frequency of the timer

Postby mikl604 » Wed Sep 13, 2023 1:24 pm

The question remains open: how can I temporarily disable all interrupts except for the selected timer? Without FreeRTOS.

tasha6
Posts: 4
Joined: Wed Mar 13, 2024 12:15 am

Re: The exact frequency of the timer

Postby tasha6 » Wed Mar 13, 2024 12:17 am

Any luck with this?

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