SPX1276 pin connections and error codes

[Jack]

@Geoff69810

The SDO pin goes to MEGA pin 50, which is labelled as MISO, and the SDI pin goes to MEGA pin 51, which is labelled as MOSI.

Both are different naming conventions for SPI. SDI/SDO stands for serial data in/out. MOSI is Master Out Slave In and MISO is Master In Slave Out.