Two days ago I ran some tests to determine how low the voltage can be on the signal feeding GPS data to the camera and still have the camera recognize the data.

I powered the microcontroller using a variable power supply. I used the serial transmit routine I wrote to send messages to the GPS module and had it send GPS messages to the camera every second. I monitored the signal going to the camera using an oscilloscope so I could check the voltage levels. While the camera was indicating it was receiving GPS data I gradually reduced the power supply voltage.

The signal to the camera started with it going between 0 and 4.8 volts. The camera was still showing it was receiving GPS data when I had the signal levels down to a range of 0 to 2.8 volts. I am planning to operate the microcontroller at either 3.3 or 3.6 volts so I won't have any issues with the signal level going to the camera.