I had a really hard time finding how to use the Port A of the M5Grey with the Port C GPS unit. After many hours
I figured it out.
Define the pins to use:
#define APortM5DialRxPin 15 //M5Dial PortA
#define APortM5DialTxPin 13 //M5Dial PortA
#define APortM5CoreRXPin 22. //M5Grey PortA
#define APortM5CoreTXPin 21. //M5Grey PortA
Define the HardwareSerial port.
HardwareSerial GpsSerial(2);
In setup begin the serial communication
GpsSerial.begin(GPSBaud, SERIAL_8N1, APortM5CoreRXPin, APortM5CoreTXPin);
I hope this will save people a lot of time