rp2pio does not drive GPIO pins on RP2350B (Metro RP2350)

[TheKitty]

CircuitPython version: 10.0.3
Board: Adafruit Metro RP2350 (RP2350B, A2 stepping)

Problem

PIO state machines run and consume FIFO data (sm.pending goes to 0), but GPIO pins are not driven. Pins stay at ~1.6V regardless of set pins, out pins, mov pins, or sideset instructions.

Works

• digitalio drives pins correctly (0V/3.3V toggle)
• picodvi (HSTX) works correctly
• Same PIO code works on Feather RP2350 (RP2350A) with same CP version

Minimal reproduction

import board
import rp2pio
import adafruit_pioasm

test_program = adafruit_pioasm.assemble("""
.program test
.side_set 1
.wrap_target
    nop     side 1  [15]
    nop     side 1  [15]
    nop     side 0  [15]
    nop     side 0  [15]
.wrap
""")

sm = rp2pio.StateMachine(
    test_program,
    frequency=10_000,
    first_sideset_pin=board.D10,
    sideset_pin_count=1,
)
# D10 stays at 1.63V instead of toggling

Likely cause

GPIO function select not being set to PIO for RP2350B variant.

[dhalbert]

# D10 stays at 1.63V instead of toggling

The average voltage on a 50% duty cycle pin is 3.3V/2 = 1.65V, so that makes sense if the measurement instrument is averaging. Did you put a scope or logic analyzer on the pin to look at the waveform? What did you see on the RP2350A pin?

[TheKitty]

Closing as resolved