There are some issues I found with the connections of the Pico: GP6 is SCK, but used as MOSI, 7 is MOSI and it's used as clock and so on.
Could we make the naming for GPIO8 and GPIO9 in a way that we can see that these are used in duplicate functions (e.g. SP_MISO_UART_TX for GPIO8)
Could you please rename GPIO16 and GPIO17 with something like SOUND_TX and SOUND_RX, it's a serial connection now. It used to be for another sound module which used another protocol.
See commits for changes