I am trying to use my Raspberry Pi Pico as a slave SPI device.
How can I use the Arduino framework to assign the pins I will be using? For example I have hooked up physical pins 21, 22, 24, and 25 (RX, SCn, SCK, TX).
I am unsure of how to perform the setup. I simply want to write a single value to a register.
Can anyone point me in the right direction?