RP2040 - PIO sideset for pin direction

[jchawks]

Currently, the RP2040 PIO support covers all the hardware configuration bits except the state machine
exec control for SIDE_PINDIR: this is defined in the hardware_structs header pio.h, for PIO_SMx_EXECCTRL : SIDE_PINDIR.
The bit next to it, SIDE_EN, is supported:
The line parsing in adafruit_pioasm.py only checks for 'opt', and not 'pindirs':

elif line.startswith(".side_set"):
                sideset_count = int(line.split()[1], 0)
                sideset_enable = "opt" in line

And the corresponding StateMachine() kwargs mapping would need to be added; the support would be analogous
to the SIDE_EN arg, which is now documented as:

• sideset_enable (bool) True when the top sideset bit is to enable. This should be used with the “.side_set # opt” directive
  (https://docs.circuitpython.org/en/latest/shared-bindings/rp2pio/index.html)

... and the HAL interface already exists, in raspberrypi\common-hal\rp2pio\StateMachine.c : 321 -
already commented to indicate position of future sideset_direction ?
sm_config_set_sideset(&c, total_sideset_bits, sideset_enable, false /* pin direction */);

The idea is to support the PIO line
.side_set 1 opt pindirs.

The rest works great; very easy to use. Many thanks for the good work.

[tannewt]

This is related too: https://github.com/adafruit/Adafruit_CircuitPython_PIOASM

[jchawks]

Thanks - I'll add the request this over there as well, linking back to here.

[jepler]

would you like to take a stab at adding it?

[jchawks]

Sure: I found a workaround for this project, but would like to do so for upcoming designs. I'm a github noob (lifelong member of the 'other' team (SVN) 😉 ) but will do my homework on how this works. Will have something in a few days...

[tannewt]

This is a good git tutorial: https://learn.adafruit.com/contribute-to-circuitpython-with-git-and-github