I added a 6 pin port on the RFM2Pi board that can be used for a number of applications. The port has GND, D3, D7, D6 and VCC routed, and by no coincidence matches perfectly the pinout of the Digole 0.96″ OLED Serial display that I toyed with previously. The OLED PCB is exactly the same size as the RFM2Pi board, and since I use the flat crystal version of the RFM12B radio module, the two can be “sandwiched” together:
I added some basic test functionality to the firmware, it displays the current configuration and the last packet source, RSSI and ACK status. RSSI is calculated using @tht’s method as per this post. The code can easily be extended to visualise emonTX power readings for example. The updated PCB layout is on github.