So I have rolled my own board based on the ATMEGA1284P QFN Chip. I am trying to drive a 4d Systems display with it over software serial and every command is timing out (no ack seen by the display). I piggy-backed off the display's TX pin and I see the acks coming in just as fast as I am sending the commands. I have verified the correct pins. I am using the AVR Developers pinout for the chip. I am using arduino v1.5 and have made the 4D Systems suggested modifications to the SoftwareSerial.cpp for the TX sending out a 0x00 before any other character.
I have simplified the situation down to just trying to make a software serial loopback using the following code:
SoftwareSerial debugSerial = SoftwareSerial(21,20);
digitalWrite(30,HIGH); //On Board LED for visual aid
delay(100); //for led blink
I plugged the usb serial TXO into 21, and RXI into 20.
I get nothing. I haven't tried manually sending anything out of the debugSerial because the display worked fine at receiving the commands. So the issue surrounds SoftwareSerial RX.
Any thoughts? I have tried multiple pins but I thought the new SoftwareSerial library used any PCINT pin. Am I mistaken?