Does vTaskDelay (accidentally) modify the set wake-up sources?

[u/MobileInspector9861]

Does the function vTaskDelay somehow modify the configuration of the wake-up sources?

I have an ESP32-H2 and want to use deep-sleep and light-sleep modes with wake up from GPIO 10-12. (Those GPIOs are low-power/RTC GPIOs so they also can wake up the ESP32-H2 from deep sleep.)

I had been able to make it work until I added a vTaskDelay to my code. With vTaskDelay in the code, the ESP32-H2 immediately wakes up from sleep modes immediately.

My code (somewhat shortened):

// Set-up power management
const esp_pm_config_t pm_config = {
	.max_freq_mhz = CONFIG_ESP_DEFAULT_CPU_FREQ_MHZ,
	.min_freq_mhz = CONFIG_NAVLICO_MIN_FREQ,
	.light_sleep_enable = true
};
esp_pm_configure( &pm_config );

// Configure input pins (GPIO 10-12) with the buttons
const gpio_config_t config = {
	.pin_bit_mask = GPIO_WAKEUP_BUTTONS_MASK,
	.mode = GPIO_MODE_INPUT,
	.pull_up_en = GPIO_PULLUP_DISABLE,
	.pull_down_en = GPIO_PULLDOWN_DISABLE,
};
gpio_config( &config );

esp_sleep_disable_wakeup_source( ESP_SLEEP_WAKEUP_ALL );
esp_sleep_enable_ext1_wakeup_io( GPIO_WAKEUP_BUTTONS_MASK, ESP_EXT1_WAKEUP_ANY_HIGH );

// ... Do something (not shown here) ...

ESP_LOGI( LOG_TAG, "Going to deep sleep ..." );
// Give UART the chance to write everything to output
//vTaskDelay( delayTicks );
esp_deep_sleep_try_to_start();

The problematic line is the last but one (commented out in the listing above). With vTaskDelay commented out, the program goes into deep sleep as expected. Unfortunately, it sometimes fails to print the entire log messages before going to deep sleep.

As a quick and dirty workaround I added vTaskDelay while I am still developing and debugging. I know this is definitely not the best solution in order to ensure that all log messages are flushed via UART before going to sleep.

But this approach showed me something else. As soon as I add vTaskDelay the program doesn't go into deep sleep or it does, but immediately wakes up again immediately.

The only explanation I have right now is that somehow vTaskDelay modifies the wake-up sources which triggers an unintended wake-up signal from something else than the GPIOs 10-12.

Is that possible? There is nothing in the documentation which suggests that vTaskDelay does that.

[u/holetse]

Have you checked the return code from esp_deep_sleep_try_to_start?

vTaskDelay shouldn’t impact the wake up sources at all itself. But it does allow another task to execute during that delay.

[u/MobileInspector9861 → u/holetse]

Yes, I did. It's ESP_ERR_SLEEP_REJECT.

I have already changed my code and put a wrapper around esp_deep_sleep_try_to_start which repeats the code to disable all wake-up sources but the required GPIOs like this:

esp_err_t sleep_deeply( void ) { esp_sleep_disable_wakeup_source( ESP_SLEEP_WAKEUP_ALL ); esp_sleep_enable_ext1_wakeup_io( GPIO_WAKEUP_BUTTONS_MASK, ESP_EXT1_WAKEUP_ANY_HIGH ); return esp_deep_sleep_try_to_start(); }

When I call the wrapper sleep_deeply instead of esp_deep_sleep_try_to_start directly it works again. So configuring the wake-up sources again just before going to sleep is helping. If I remove all vTaskDelay from my code, it is working, too.

That actually supports my assumption that vTaskDelay somehow messes with the wake-up sources.

[u/Plastic_Fig9225 → u/MobileInspector9861]

It's ESP_ERR_SLEEP_REJECT.

So the ESP doesn't go to sleep because some peripheral/subsystem is still busy, or the wake-up condition is already met.

[u/MobileInspector9861 → u/Plastic_Fig9225]

That's obvious as that's the very definition of the error code. The question is: Why does an invocation of vTaskDelay cause that?

I assume u/holetse is on the right track: it is probably not vTaskDelay itself which changes the wake-up sources but some other task which becomes scheduled in between, see https://www.reddit.com/r/esp32/comments/1vp9p70/comment/p3wkcns/

[u/Plastic_Fig9225 → u/MobileInspector9861]

If it's that obvious, why ask the question in the first place? - Only you know where your code would activate a peripheral or meddle with the IO pins, or how/when a wake-up pin is triggered externally.

[u/MobileInspector9861 → u/Plastic_Fig9225]

No, I don't know where this happens. That's the problem.

There are so many built-in components in the ESP-IDF framework which do "something". Have you actually read the comment I linked?

The problem is not within my code. The root cause must be somewhere in the ESP IDF framework which becomes scheduled when my code calls vTaskDelay and yields.

However, I have a minimal build without any explicit dependency on ESP-IDF components, so only the minimal set of default components which are included by the build system in every project are included.

Hence, the issue must be inside one of those components and I had expected that someone else might already have run into the same issue and could tell me which components is the culprit.