The PWM module now detects if the pin is open drain and if so switches it
to hardware open drain before starting the PWM.
The code that was explicitly turning off the open drain output during PWM
is also removed.
Together these changes allow driving external transistor high-current
switches with PWM.
Signed-off-by: Trammell hudson <hudson@trmm.net>
The PWM driver uses a double buffer for the PWM timing array, one in
current use and the other one to update when changing duty parameters.
The issue was that once the duty parameters were changed the updated buffer
was applied immediately without synchronising to the start of the PWM
period. By moving the buffer toggling/swapping to the interrupt when the
cycle is done there are no more glitches.
Note: the uncrustify configuration is explicitly set to 'add' instead of
'force' in order not to alter the comments which use extra spaces after //
as a means of indenting text for clarity.
The PWM at full value was not considered as an "active" channel so if no
other channel was used the timer used to mange PWM was not started. So
when another duty value was set the PWM timer restarted and there was a
visible glitch when driving LEDs. Such a glitch can be seen with the
following code (assuming active-low LED on pin 0):
p = machine.PWM(machine.Pin(0))
p.duty(1023) # full width, LED is off
p.duty(1022) # LED flashes brightly then goes dim
This patch fixes the glitch.
This is to keep the top-level directory clean, to make it clear what is
core and what is a port, and to allow the repository to grow with new ports
in a sustainable way.
