Especially at high frequencies the achieved one is only close,
but that's entirely sufficient for our purposes.
Test: the PWM frequency on the scope should be similar to the
one configures in the board file with DEFINE_HEATER().
Works very nicely from full off (M106 S0) to full on (M106 S255).
Test: M106 should work now as expected. M106 S0 should turn full
off, M106 S255 should turn full on, both without any spike on the
scope.
Currently at a fixed frequency of 1 kHz and with a fixed duty
cycle of 10%, but PWM does work.
As it turns out, PIO0_11 is not usable for PWM, because its timer
is already in use for the Step timer, and had to be disabled for
Gen7-ARM.
Test: define a heater in board.gen7-arm.h and a square signal
of 1 kHz with 10% duty cycle should appear on the heater pin.