Fixes ESP32-S2 CDC Debug Logging

[SuGlider]

Description of Change

When using ESP32-S2 with USB CDC and debug output is set also to go to the CDC (Serial.setDebugOutput(true)), the S2 freezes after a few line of logging.

This issue only occurs with the ESP32-S2. It works fine with ESP32-S3 and CDC.

Tests scenarios

Tested with this sketch on the ESP32-S2 and ESP32-S3. IDE must set USB CDC On Boot: "Enabled"

#include <Arduino.h>

static void test_taskfunc(void * p)
{
    uint32_t tasknum = (uint32_t)p;

    while (true) {
        log_i("This is task instance %u running...", tasknum);
        
        delay(10 * random(1, 10));
    }
}

void setup()
{
    Serial.begin(115200);
    Serial.setDebugOutput(true);
    delay(2000);
    Serial.println("\n==============\nStarting...\n");
    log_e("Starting with LOGs.");
    Serial.println("==============\n\n");
    delay(750);

    for (auto i = 0; i < 5; i++) {
        TaskHandle_t th;

        // Created tasks all need to have different priorities in order to trigger lockup
        UBaseType_t taskPrio = 1 + 2 + i;

        if (pdPASS == xTaskCreate(test_taskfunc, "test_taskfunc", 4096, (void *)(i + 1), taskPrio, &th)) {
            log_i("Task instance %u created with priority %u", i+1, 3 + i);
        } else {
            log_e("Task instance %u creation FAILED", i+1);
        }
    }
}

void loop()
{
    log_i("This is the main loop running...");

    delay(10 * random(1, 10));
}

Related links

Fixes #6766

[avillacis]

The good news: After applying this change, on my ESP32-S2 dev board, redirecting debug output to the USB CDC does not hang the sketch anymore. The sketch keeps running without interruption.

The (tolerably) bad news: It appears that some messages are not completely flushed to the opened serial terminal, so that the strings appear truncated. However, when more data is written with the log_X functions, the rest of the apparently-truncated string is emitted before the next message appears.

[SuGlider]

The (tolerably) bad news: It appears that some messages are not completely flushed to the opened serial terminal, so that the strings appear truncated. However, when more data is written with the log_X functions, the rest of the apparently-truncated string is emitted before the next message appears.

I guess that this happens only because the example has 2 tasks, writing to the CDC at the same time and one may interrupt the other while still writing the log, character by character, truncating the previous message by another task.

Maybe the best way to solve it is by creating a Message Queue within the sketch and a task that consumes this queue, printing one log message at a time, in order to make sure that it will not get truncated. In this case the tasks shall enqueue the messages using a specific API, which could also sort them by some critical ordering method, for instance.

[VojtechBartoska]

PR Update: Investigate why function tud_cdc_n_write_available freeze?

[brentru]

@SuGlider @VojtechBartoska I am experiencing a similar lockup on the latest BSP (due to setDebugOutput(true) which I need for debugging). This PR resolves this issue.

What is the status of this PR in general, and the status of it making it into the next release?

[SuGlider]

@brentru - I'll take a look and check it. But in general, I'd say that the PR is ready for review.

[paclema]

I can confirm too that this helps with ESP32-S2! When is it planned to be merged?

[VojtechBartoska]

@SuGlider what about this PR, can it be reviewed or more work is supposed to be done on this?

[github-actions]

Warnings

⚠️

Some issues found for the commit messages in this PR: the commit message "Fixes ESP32-S2 CDC Debug Logging": summary looks empty type/action looks empty Please fix these commit messages - here are some basic tips: follow Conventional Commits style correct format of commit message should be: <type/action>(<scope/component>): <summary>, for example fix(esp32): Fixed startup timeout issue allowed types are: change,ci,docs,feat,fix,refactor,remove,revert sufficiently descriptive message summary should be between 20 to 72 characters and start with upper case letter avoid Jira references in commit messages (unavailable/irrelevant for our customers) TIP: Install pre-commit hooks and run this check when committing (uses the Conventional Precommit Linter).

	Messages
📖	You might consider squashing your 5 commits (simplifying branch history).

👋 Hello SuGlider, we appreciate your contribution to this project!

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[SuGlider]

@me-no-dev - Retested. The PR is necessary to use USB OTG CDC logging in ESP32-S2.

[SuGlider]

@me-no-dev - This PR should be applied to branch master and to release/v2.x to make sure it goes to a future 2.0.15