I don't know what pins are being used for what.

[wraybowling]

An ATMEGA328P has 28 pins and it's not very clear what pins are being used for what purpose.

https://www.arduino.cc/en/Hacking/PinMapping168

If it's checked, then I'm 100% certain. If not, I'm still guessing.

Row 1

• 1
• 2 FTDI connector pin 3 (TX) seems to be backwards with RX
• 3 FTDI connector pin 2 (RX) seems to be backwards with TX
• 4 Right side LED & digital output
• 5
• 6 Left side LED & digital output
• 7 Power
• 8 Ground (only used for FTDI connector)
• 9 16MHz Crystal Oscillator clock 1
• 10 16MHz Crystal Oscillator clock 2
• 11 radial encoder top left
• 12 radial encoder top right
• 13 radial encoder bottom right
• 14 screen Data Command (DC) ((front: DC))

Row 2

• 15 screen Reset ((front: R))
• 16 screen OLED Chip Select (OLEDCS) ((front: OC))
• 17 screen Master Out Slave In (MOSI) ((front: SI))
• 18 screen Master In Slave Out (MISO) ((front: SO))
• 19 screen Serial Clock (SCK) ((front: CL))
• 20 Power
• 21 Reference Voltage
• 22 Ground
• 23 (A0)
• 24 (A1)
• 25 (A2)
• 26 (A3) radial encoder bottom left
• 27 (A4)
• 28 (A5)

Radial Encoder
top center connects to bottom left ???

[wraybowling]

Trying to find the pin for the right side LED made me crazy... So time for a damn checklist!