5VIN - Regulated 5v input. Be sure to connect to REGOUT if you are not using an external 5v voltage regulator.
RXD - Data from GPS or PC. Connect to pin 2 on Null Modem Cable.
AOUT - Audio to Radio.
REGIN - 6.5v to 28v into regulator.
PTT - connect to Push-To-Talk line on radio.
ADC1 - Analog input. Use with Temperature Sensor.
ADC2 - Analog input. Use with Temperature Sensor.
TXD - Data to GPS or PC. Connect to pin 3 on Null Modem Cable.