I see a lot of tutorials that say something like "Connect Rx of GPS to pin D1 and Tx to pin D2", but I'm wondering what communication protocol is being used to talk to the GPS, or is it just digital signals and I can use any digital pin and just modify the pinout using the IDE? Thanks in advance.
I could be wrong (as I've not used a GPS with an Arduino), but the GPS modules tend to communicate using NMEA sentences. These are plain ASCII text strings that contain a sequence of comma separated values. If you Google NMEA 0183 you should get lots of information. Here's one site.
Most GPS are using 9600 baud serial
what communication protocol is being used to talk to the GPS
Almost always plain ASCII text, TTL-RS232 serial.
Use either the hardware serial port and Serial.print() or one of the software serial packages NeoSWserial, Altsoftserial or SoftwareSerial.
Check the documentation and obey the rules for which pins can be used for TX and RX.
freebird4446:
I see a lot of tutorials that say something like "Connect Rx of GPS to pin D1 and Tx to pin D2", .
Hopefully, you never really saw that. Pin D1 is hardware serial. While pin D2 is not, it may be used for software serial. Whichever way you go, you need to make up your mid, rather than have a bit of both.
freebird4446:
I see a lot of tutorials that say something like "Connect Rx of GPS to pin D1 and Tx to pin D2", but I'm wondering what communication protocol is being used to talk to the GPS, or is it just digital signals and I can use any digital pin and just modify the pinout using the IDE? Thanks in advance.
If by 'talk to the GPS' you mean how do you send commands to the GPS, then sometimes this is in serial ASCII text and sometimes in serial non-ASCII HEX style data.
Depends on the GPS and what commands you want to send to it.