This is an Arduino wrapper for MicroAPRS in SerialMode from https://github.com/markqvist/MicroAPRS

Serial Protocol is enabled in https://github.com/markqvist/MicroAPRS/blob/master/Modem/config.h

change from

#define SERIAL_PROTOCOL PROTOCOL_SIMPLE_SERIAL
//#define SERIAL_PROTOCOL PROTOCOL_KISS

to

//#define SERIAL_PROTOCOL PROTOCOL_SIMPLE_SERIAL
#define SERIAL_PROTOCOL PROTOCOL_KISS

make it new and flash the firmware on you Arduino238p

As an example the code will transmit the humidity and temperature values from an DHT11 sensor as Comment via APRS

APRS is a registered trademark of APRS Software and Bob Bruninga, WB4APR.