I found the same code can work with both P and PB boards. if we line up our pinout properly we might be able to use existing atmega328p boards as a quick way test many (6x) talking together.

what do you all think worth switching things up a bit?

//    digitalWrite(0)         //--> D0  -- TX Serial OUT
//    digitalWrite(1)         //--> D1  -- RX Serial IN
//    digitalWrite(2)         //--> D2  -- RADIO_IRQ RFM_INT
//    digitalWrite(3,LOW);    //--> D3  --LED_0
//    digitalWrite(4,LOW);    //--> D4  --LED_1
//    digitalWrite(5,LOW);    //--> D5  --LED_2
//    digitalWrite(6,LOW);    //--> D6  --LED_3
//    digitalWrite(7,LOW);    //--> D7  --LED_4
//    digitalWrite(8,HIGH);   //--> B0  --LED_5
//    digitalWrite(9,HIGH);   //--> B1
//    digitalWrite(10,HIGH);  //--> B2  --SSO  RFM_CS
//    digitalWrite(11,HIGH);  //--> B3  --MOSI RADIO AND PROGRAMMING
//    digitalWrite(12,HIGH);  //--> B4  --MISO RADIO AND PROGRAMMING
//    digitalWrite(13,HIGH);  //--> B5  --SCK  RADIO AND PROGRAMMING
//    digitalWrite(14,LOW);   //--> C0  --LED_6
//    digitalWrite(15,LOW);   //--> C1  --LED_7
//    digitalWrite(16,LOW);   //--> C2  --LED_8
//    digitalWrite(17,LOW);   //--> C3  --LED_9
//    digitalWrite(18,LOW);   //--> XX  --LED_10
//    digitalWrite(19,LOW);   //--> XX  --LED_11
//    digitalWrite(20,LOW);   //--> XX  --BATTERY_SENSE
//    digitalWrite(21,LOW);   //--> XX
//    digitalWrite(22,LOW);   //--> XX
//    digitalWrite(23,LOW);   //--> E0
//    digitalWrite(24,LOW);   //--> E1
//    pinMode(A2, INPUT_PULLUP); //-->25 (ALSO C2)