Summary

This PR adds board support for the Seeed Studio XIAO RP2040 Plus to the rp2 port.

It introduces a dedicated SEEED_XIAO_RP2040_PLUS board definition with:

• board metadata
• RP2040 Plus pin mappings
• 2 MB flash configuration
• onboard WS2812/NeoPixel and power-enable definitions
• corrected dual-I2C defaults for the Plus board:
  • I2C0 on GPIO20/GPIO21
  • I2C1 on GPIO6/GPIO7

The main goal is to make the board usable as a first-class MicroPython target with correct default peripheral mappings for the hardware actually routed on the XIAO RP2040 Plus.

Testing

Tested on a Seeed Studio XIAO RP2040 Plus board.

The following were verified with locally built MicroPython firmware for SEEED_XIAO_RP2040_PLUS:

• firmware builds successfully for the rp2 port
• board boots and enters the MicroPython REPL
• I2C0 works on GPIO20/GPIO21
• I2C1 works on GPIO6/GPIO7
• SPI works on the expected board pins
• UART works on the expected board pins
• GPIO tests passed
• ADC tests passed
• PWM tests passed
• onboard LED test passed
• onboard NeoPixel/WS2812 test passed

I2C was specifically re-checked after fixing the bus/pin mapping to match RP2040 hardware function constraints.

Trade-offs and Alternatives

This change is board-local and does not alter shared rp2 port behavior for other boards.

The only meaningful alternative would have been to keep the previous I2C mapping, but that would leave one of the buses assigned to pins that do not match the intended MicroPython hardware I2C instance usage for this board. The submitted mapping reflects the actual validated working configuration on hardware.

Generative AI

I used generative AI tools when creating this PR, but a human has checked the
code and is responsible for the code and the description above.