[Scheduling] Critical task with source_tim6 timer doesn't work

[pierre-haessig]

Describe the bug

As a follow up of owntech-foundation/examples#57 where the critical task of the Blinky example cannot start unless the tim6 source is specified.

I've created a Blinky example with a simple critical task with timer source set to source_tim6, see blinky+critical branch https://github.com/pierre-haessig/owntech-examples/blob/blinky%2Bcritical/src/main.cpp. However , I believe that the critical task is not starting. Perhaps timer 6 is not initialized?

To Reproduce
Steps to reproduce the behavior:

1. Load blinky example
2. Replace main.cpp by the one from the blinky+critical branch at e0841bd commit https://github.com/pierre-haessig/owntech-examples/blob/e0841bd5cbac7a21b99c3d4bf70e54d092c9f8c8/src/main.cpp
3. Build and Upload code

Expected behavior

The critical task, if it runs at least one, should set the boolean flag flag = true;

Then the loop_background_task is blinking the LED at a speed which depends on the flag. If flag were true, the blinking should be fast (100ms). However, it is slow (1000 ms), proving that flag=false.

[pierre-haessig]

As an experiment, I've tried to use the code of the SPIN/PWM/duty cycle setting example.

That is the critical task is created as task.createCritical(loop_critical_task, 500, source_hrtim);.

However, first the following three lines are added at the start of the setup routine:

/* Set frequency of PWM */
spin.pwm.initFixedFrequency(200000);
/* Timer initialization */
spin.pwm.initUnit(PWMA);

/* Start PWM */
// spin.pwm.startDualOutput(PWMA);

→ the critical task runs! More precisely it runs once the spin.pwm.initUnit(PWMA); is executed, while the startDualOutput is not necessary.

Here is the updated main.cpp