This follows the pattern of other peripherals (I2C, SPI) to specify the
pins using pin objects instead of a pair of GPIO port and pin number. It
makes it easier to customise the UART pins for a particular board.
Previously, SPI was configured by a board defining MICROPY_HW_ENABLE_SPIx
to 0 or 1. Now, the board should define MICROPY_HW_SPIx_SCK, MISO, MOSI
and NSS. This makes it the same as how I2C is configured.
To build:
make BOARD=ESPRUINO_PICO
To deploy: short the BOOT0/BTN contact on the back of the board (eg by
drawing over it with a graphite pencil), then hold down BTN while
inserting the board into the USB port. The board should then enter DFU
mode, and the firmware can be downloaded using:
make BOARD=ESPRUINO_PICO deploy
