Documentation request: Ticker, attach_ms and attach_ms_scheduled

[d-a-v]

Hint: Ticker/TickerFunctional.ino example
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[tom-ch1]

The linked conversation does not help. It points to a matrix room with discussions of various things. I'd love to see the discussion here, so that anybody can follow it

[tom-ch1]

Here's the documentation of Ticker: https://arduino-esp8266.readthedocs.io/en/latest/libraries.html#ticker

It is currently not recommended to do blocking IO operations (network, serial, file) from Ticker callback functions. Instead, set a flag inside the ticker callback and check for that flag inside the loop function.

Here's the source code of attach_scheduled:

// callback will be called at following loop() after ticker fires

As there is no documentation other than the source code and the examples, one would deduce that using attach_scheduled resolves the warning given in the recommendation

Is that correct?

According to the Example TickerFunctional.ino, there is no need for any funcion call inside loop(), and nevertheless, the callback is called inside loop()

Is that correct?

[mcspr]

As there is no documentation other than the source code and the examples, one would deduce that using attach_scheduled resolves the warning given in the recommendation

Is that correct?

Right, _scheduled are the exception. Note the code flow - scheduled funcs are called only after loop() normally returns , or when yield() suspends loop() and our user task to run SDK tasks

Arduino/cores/esp8266/core_esp8266_main.cpp

Lines 247 to 251 in 1662248

	extern "C" void __loop_end (void)
	{
	run_scheduled_functions();
	run_scheduled_recurrent_functions();
	}

Arduino/cores/esp8266/core_esp8266_main.cpp

Lines 262 to 263 in 1662248

	loop();
	loop_end();

edit: disregard the yield() bit, normal scheduled funcs can only run after loop() normally returns.
there are recurrent ones that do both, but this is not the type of scheduled function that ticker uses

As there is no documentation other than the source code and the examples, one would deduce that using attach_scheduled resolves the warning given in the recommendation

Is that correct?

attach_ms callback would execute whenever SDK decides it is time for the timer to expire and in SDK context. That happens outside of user task, after yield() gives SDK task a chance to run. For attach_ms_scheduled we effectively do schedule_function([user_callback]() { user_callback(); })