cannot send command over serial from a redboard artemis Serial1 to Adafruit ultimate GPS

[jerabaul29]

I am using the core v1.2.3.

I am hitting a strange issue. I am using an Adafruit ultimate GPS (which I have used many time before with Arduino Unos, Megas etc), and an Artemis RedBoard. It is the first time I try to use both together, but I have used each of these components in many projects before.

My setup:

• Redboard -> GPS
• TX1 -> RX
• RX1 -> TX
• GND -> GND
• 3.3V -> Vin (as recommended; I have also tried to 3.3V)

My issue is the following: I get GPS NMEA strings just fine to the Redboard, but somehow it seems like I cannot send commands to the GPS. I have tried sending commands to get antenna status, change parameters of the GPS, etc, with no success. Any possible reason you could think of that would case TX1 signals to be wrongly formatted / somehow fail when fed to the GPS RX? I obviously use the right ports, baudrate etc (as I can read NMEA strings from the GPS, such as GPRMC strings, just fine). I have tried plenty of variations in the code, tried to send the string by hand vs. with the adafruit library, no way I get the GPS to receive a command.

[jerabaul29]

(the setup and wiring look like the drawing there: https://github.com/jvoermans/Wind_Input_V1/tree/logger_version_jr ; I am not very good at serial protocols, is there a possibility that there is some sort of parity / stop or start bits / other that may be set in a way or another that confuses the GPS serial receiver?)