Support for Raspberry Pi RM2 wifi / ble module

[anecdata]

Would need CircuitPython API to select the MCU pins to use.

We also may want to consider adding ssl to boards with enough resources that would not ordinarily have it (this would also expand the set of boards that could use WIZnet ethernet as an SPI peripheral with ssl).

I don't see mention of this module on the Raspberry Pi site, but it is incorporated in 3rd-party products, for example @pimoroni RM2 breakout and Pico Plus 2 W.

Related:
CircuitPython Bump cyw43-driver module to v1.0.4 plus to match SDK 2.0.0. #9775
MicroPython Pico 2 W changes #16057

[eightycc]

The RM2 module incorporates the same mux'ing of its DI, DO, and IRQ pins as the Pico Plus 2 W so building a CP board port for a Pico Plus 2 board with the module SP/CE attached should be straightforward.

Of course that approach leads to a proliferation of board ports, so some means of separately supporting RM2 might be a good thing.

[eightycc]

Pico SDK 2.0.0 hard codes the pin numbers used for the CYW43439 gSPI interface, so changing CYW43_PIN_WL_... will have no effect. The develop branch of the SDK corrects this.

[dhalbert]

Are there boards that need the pin numbers to be changed? Or can we wait for the pico-sdk changes to be put in a release? We can move up the submodule commit if necessary.

[eightycc]

@dhalbert All of the RP2350 boards that include an RM2 that I've looked at follow the RP2040 Pico W pin assignments so they are not affected. It does become an issue with RM2 breakouts. For example, the Pimoroni Pico Plus 2 attaches an RM2 breakout with its SP/CE connector that utilizes pins 32, 33, 34, 35, and 36.

I do not recommend switching to the SDK develop branch at this time. I tried it and got stuck in build issues.