PIO: Use the same Pin for input and output.

[robert-hh]

It may be that by PIO skill faded a little bit, but I'm fighting to use the same pin in a state machine for input using the in_(pins, 1) statement and output with out(pins, 1). Even setting the direction does not seem to work. in_() works, but no data is shifted out. Shifting data out at a different pin works. It using the same pin impossible, or do I just have a brain block?

[GitHubsSilverBullet]

Shifting data out at a different pin works. It using the same pin impossible, or do I just have a brain block?

Using the same pin would mean to dynamically change pin and pindir.
Have you tried SET(pindir) to IN and then receive,
and then SET(pindir) to OUT and then send?

[robert-hh]

I tried indeed set(pindir) and pre-configuring the Pin in various modes. The strange thing is, that I have a driver for DHT22 that uses the same pin for in_() and setting that pin using set(pins,..). But that is not a feasible approach with varying data.

[robert-hh]

After talking I found a combination of settings that work. Both set_init and out_init have to set the respective Pin to OUT_xxxx mode,

[GitHubsSilverBullet]

And is it then possible to IN() and OUT() without changing SET(pindir) in between?

[robert-hh]

No. One has to use set(pindir) to change the direction. But I tried that before already, but without configuring out_init. The header of the asm_pio code now looks as:

    @rp2.asm_pio(
        in_shiftdir=rp2.PIO.SHIFT_LEFT,
        out_shiftdir=rp2.PIO.SHIFT_LEFT,
        autopull=False,
        autopush=False,
        out_init=rp2.PIO.OUT_LOW,
        set_init=rp2.PIO.OUT_HIGH,
        sideset_init=rp2.PIO.OUT_LOW
    )

and the state machine instantiation includes in_base=data, out_base=data, set_base=data, , with data being the pin of interest.