Sure, here are the specific pins on both U1 and U2 that you need to connect to facilitate SPI communication:
On U1 (Adafruit's 3857):
MISO (Master In Slave Out) is Pin 13, labeled as "MI".
MOSI (Master Out Slave In) is Pin 12, labeled as "M0".
SCK (Serial Clock) is Pin 11, labeled as "SCK".
SS (Slave Select) can be any GPIO pin you select, but it is often done with D10 (Pin 23), labeled as "D10".
On U2 (RFM95W)
MISO corresponds to Pin 2, labeled as "MISO".
MOSI corresponds to Pin 3, labeled as "MOSI".
SCK corresponds with Pin 4, labeled as "SCK".
NSS (which stands for "Negative Slave Select" and essentially fulfills the same role as SS) corresponds to Pin 5, labeled as "NSS".
Therefore, the connections on your Flux project should be:
U1-MI (Pin 13) to U2-MISO (Pin 2).
U1-MO (Pin 12) to U2-MOSI (Pin 3).
U1-SCK (Pin 11) to U2-SCK (Pin 4).
And you will assign a digital pin for U1's Slave Select (like D10 on U1) and connect it to U2-NSS (Pin 5).
Remember, you might need to reconfigure these connections in your microcontroller's software, especially the Slave Select pin.
Also, keep in mind the voltage level compatibility between the modules. Both Adafruit's 3857 and the RFM95W run on 3.3V, so you shouldn't encounter any issues on that front.
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