On the Pico the layer is almost empty: analogio, pwmio, busio I2C/SPI and microcontroller are guarded by arch == "avr", and time/supervisor/alarm use hal.timer

[begeistert]

analogio.py:19, pwmio.py:19, busio.py:42 and microcontroller.py:15 guard their imports with __CHIP__.arch == "avr", and rp2040/rp2350 declare arch = "arm" (pymcu/chips/rp2040.py:27). time.py, supervisor.py and alarm.py reach for pymcu.hal.timer, which raises CompileError on anything but AVR or PIC (hal/timer.py:47-48). On a Pico you get digitalio and busio.UART and little else. CHANGELOG.md:15 announces "RP2040 support: board/digitalio/busio dispatch by architecture", true for two of those three. raspberry_pi_pico.py defines no usable board.LED for the Pico W.

From the read-only audit of the layer against CircuitPython (2026-09-14), Uno-class boards first.