RMT_TX Module Strange Behaviour When Enabling and Disabling Inside a Method. (IDFGH-14878)

[Dawid-Wawrzynczyk]

Answers checklist.

• I have read the documentation ESP-IDF Programming Guide and the issue is not addressed there.
• I have updated my IDF branch (master or release) to the latest version and checked that the issue is present there.
• I have searched the issue tracker for a similar issue and not found a similar issue.

IDF version.

ESP-IDF 5.4.0

Espressif SoC revision.

ESP32-S3

Operating System used.

Windows

How did you build your project?

VS Code IDE

If you are using Windows, please specify command line type.

PowerShell

Development Kit.

ESP32-S3-WROOM-1

Power Supply used.

USB

What is the expected behavior?

Both direct calls and method calls should work the same, at the end of the day, a method is only a fancy wrapper with a name.

Direct:

rmt_disable(channel);
rmt_enable(channel);

Method:

void cancel_rmt_transmission(rmt_channel_handle_t channel) {
    rmt_disable(channel);
    rmt_enable(channel);
}

My RMT module should stop the current transmission and continue onto any other queued transmissions, which can be queued like so:

rmt_transmit(parameters); //transmission 1
rmt_transmit(parameters); //transmission 2
rmt_transmit(parameters); //transmission 3

What is the actual behavior?

The direct call inside my main task where all RMT stuff is done works, correctly. In my case, I have stepper motors which are driven by the RMT module, so when I do:

rmt_disable(channel);
rmt_enable(channel);

Everything works as expected, if the RMT was processing the transmission 1, it should move directly onto transmission 2.

The story is a bit different if I call my method...

void cancel_rmt_transmission(rmt_channel_handle_t channel) {
    rmt_disable(channel);
    rmt_enable(channel);
}

I call the method inside the same task, instead of a direct call:
cancel_rmt_transmission(channel)

And yes the transmission is stopped... but because my RMT drives my motors, I can clearly see that the motors now 'skip' all the other transmissions, instead of following the encoder data which I previously made for them, they just move onto the transmission for a split second, sharply jump into some random position and stop.

Steps to reproduce.

1. Create an RMT channel
2. Create a method to cancel the transmission like so:

void cancel_rmt_transmission(rmt_channel_handle_t channel) {
    rmt_disable(channel);
    rmt_enable(channel);
}

3. Create a FreeRTOS Task which will handle RMT commands. Create a basic loop inside the task like so:

    while (1)
    {
        if (xSemaphoreTake(semaphore, portMAX_DELAY) == pdTRUE)
        {
            //Create some condition on when to start a transmission and when to stop it
            //This will work
            rmt_disable(channel);
            rmt_enable(channel);
            //This won't
            cancel_rmt_transmission(channel);
        }
    }

Debug Logs.

More Information.

Anyone has any idea what's going on here?

I am using the new 'rmt_tx.h' module introduced in ESP-IDF 5.0

[suda-morris]

I can't think of a reason why by calling the rmt_enable/disable directly makes difference from wrapping them inside another function... Maybe the issue locates in a difference place.

What do you mean by "skip"? is the next transmission picked up or not? How did you configure the transmission "loop_count"?

Can you strip your demo to only use a simple copy_encoder and transmit multiple transactions into a queue, calling disable/enable in another function, and attach your logic analyzer to see what is really happen.

[Alvin1Zhang]

@Dawid-Wawrzynczyk Thanks for reporting, would you please help share if any updates for the issue? Thanks.