disable any background task

[0wwafa]

Board

ESP32 dev kit v1

Device Description

Classic esp32 wroom-32 devkit v1 with cp2102

Hardware Configuration

1 gpio connected to an external device

Version

v3.1.0

IDE Name

Arduino IDE

Operating System

Ubuntu 22.04

Flash frequency

40 mHz

PSRAM enabled

yes

Upload speed

921600

Description

Everything works but I need to know how to completely disable any RTOS background task EXCEPT the UART.
I made a sketch that sets an interrupt when a gpio changes then sends the timing as a single character (or 4) to the serial UART0.
Since the pulses on the gpio are coming at a very fast rate (up to 57 microseconds apart), as the pulse arrives and it's measured, I send it to the serial port. Everything works but every now and then (like 2 times in 30 seconds) I miss pulses and I get a delay of around 1.2 milliseconds!
It's not my program and it's not the source.
it's like there is something locking up the device for that time.

Is there a way to disable anything except the "Serial" ?
In the setup of my sketch I only have one single interrupt on the gpio rising edge.

The crazy thing is that I can easily get those pulses using an ft232r device (which unfortunately is more imprecise than the esp32).
I would love to do the same with the esp32 but it seems there is a problem.

Note:
if I use slower timings on the source device this happens less.

Note2:
I tried using a smaller transmit buffer 8,16,32 and 64 bytes .. they all work and they all have the same problem...

Sketch

Unfortunatey I can't provide the sketch. It would be too complex.
But there is a similar project called "Tapuino Next" which uses the same method.
They are unaware of the problem because the use slower speeds though.

Debug Message

There are no relevant debug messages to show.

Other Steps to Reproduce

I am not sure where the problem lies...
perhaps creating an interrupt every 60 microseconds and then send a single byte on the serial prot could trigger the problem.
I can try that if you can't provide a way to disable any background task (which would IMHO solve the problem)

I have checked existing issues, online documentation and the Troubleshooting Guide

• I confirm I have checked existing issues, online documentation and Troubleshooting guide.

[0wwafa]

To be exact: the "event" happens every 17.8 seconds!

I measured by sending constant pulses from the source and timing when I was losing one.
I am losing one every 17.8 seconds and it's not obviously because of my code.

Something happens inside RTOS/ESP32 around that time... and whatever is going on stops for 1-2 milliseconds.

[0wwafa]

if it helps, the event happens after 7140 interrupts (received pulses) but it can be unrelated to interrupts.

I really don't know why this happens but this will make any project streaming data from timed pulses miss out.

[0wwafa]

the only reference to 17 or 18 seconds I found is this and it seems related: esp-rs/esp-hal#922

[me-no-dev]

You should use hardware peripheral for this. RMT is a good choice in this case. It will give you precise length of each pulse. You can not just kill all background tasks in RTOS

[0wwafa]

perhaps related to this too: https://www.reddit.com/r/esp32/comments/wfuari/esp32_freezes_at_random_intervals_just_seconds/

[0wwafa]

UPDATE: I made another test and I set the cpu at 160 mHz instead of the default 240mHz and the problem does not show up.

I think it might be something related to the watchdog or something similar.
With a tight code and very fast interrupts probably something happens and it should not.
Or the cpu overheats or just f*cks up for some reason.

The fact that the problem happens only at 240mhz is proof that itàs not related to my code.

[0wwafa]

You should use hardware peripheral for this. RMT is a good choice in this case. It will give you precise length of each pulse. You can not just kill all background tasks in RTOS

Please, don't change the subject. I want to use a simple IRQ. What's wrong with that?
Also RMT, as far as I know, does not allow me to stream data indefinately.

My program is simple:

RISING EDGE >> IRQ >>> SEND BYTE ON SERIAL PORT AT 921600

the loop() is empty (for now)
in the setup I just setup the irq and in the irq routing there is also the serial send.
There is NO WAY this should not work on any reasonable system.

And it works at 160 mHz. At 240 mHz there is the glitch.

[me-no-dev]

I want to use a simple IRQ. What's wrong with that?

Nothing wrong if you accept the consequences. It's a simple thing in non-RTOS environment. I suggested a way to get the result you want.

the loop() is empty (for now)

This is not a good approach on RTOS. Better add delay(ms) inside to tell the scheduler that it should not switch to that task.

Also RMT, as far as I know, does not allow me to stream data indefinately.

You can have a look at this example on how to mimic callback with a task, but if the timing of the serial bytes is not critical, you could in the loop wait for some pulses from RMT and send them out to Serial.

Everything thus far is just a theory from my side, because you did not provide any code to see what it's actually doing or be able to replicate the problem.

[0wwafa]

UPDATE: it happens also at 160 mHz.

I wish to use the raw power of esp32, but it seems RTOS is ruining the party (and not only for me).

I can't believe that a simple program like this goes flawlessly for 18 seconds then glitches (not my program fault).

This is really unacceptable.

P.S.
RMT is even more complex and gives people a lot of problems (probably for the same reason since they use it for very fast logging)

Please solve this!

[me-no-dev]

Without minimal code to replicate the issue, there is nothing we can do. Basic description of the input signal is also needed.

[0wwafa]

Just create a simple interrupt on a gpio and measure the distance between two pulses of a clock.

If the clock has a period of less than (let's say) 800 microseconds, you will SKIP pulses.
I don't know how to code that (yet) but it's pretty simple.

My code would be useless to you because it's monitoring an external source.
But the problem is NOT in the code.

You can check this code which does the same: https://github.com/sweetlilmre/TapuinoNext/blob/main/src/ESP32TapRecorder.cpp

The recoder WILL skip pulses for the same reason.