Adafruit Ultimate GPS on Matek F405 Wing V2 no GPS status


I’m trying to get a MT3339 based GPS working with Ardupilot, specifically a Adafruit Ultimate GPS Breakout V3 on a Matek F405 Wing V2 board.

I verified, that the GPS is connected correctly on Serial3 by using the passthrough feature and I can see the NMEA messages in Terminal.

The issue is that even if the GPS has a 3D Fix indicated by LED, Ardupilot’s Pre-Arm check fails
with “AHRS - Waiting for Home”, “EKS3 not started”. Indicator on HUD is “GPS: No GPS”.

Serial Port is configured as GPS with correct baudrate of 9600. I tried GPS_TYPE as “Auto”, “NMEA”, “HemisphereNMEA” and I was not able to get it to the point that I would see some “GPS: No Fix” or whatever on HUD.

My Question is, if the NMEA Type GPS function is part of the Firmware Limitations, i.e. NMEA_UNICORE mentioned here
. I have doubt that it is compiled into the firmware.

Thank you and Best Regards

to get nmea support you probably have to make a custom firmware for a 405 board as it wont have many features due to lack of memory.

Thank you, I’ll try.
Just to be sure, where do I find this feature selection in the regular sources, so I can build locally?

Thank you very much, it was exactly like you said. NMEA was not compiled in.
With custom firmware, I get “GPS: NO FIX” instead of “GPS: NO GPS”.

I have not tested any further yet.

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Summing up my endeavors of the past week.
If NMEA is built-in, I get a 3D FIX with the Adafruit Ultimate GPS, but it does not last long because AHRS / EKF3 regards the GPS as broken due to the 1Hz STANDARD update rate of NMEA.

09.03.2024 07:43:14 : PreArm: GPS 1: Bad fix
09.03.2024 07:43:13 : PreArm: AHRS: Not healthy
09.03.2024 07:43:01 : GPS 1: detected as NMEA at 9600 baud
09.03.2024 07:42:48 : GPS 1: detected as NMEA at 9600 baud
09.03.2024 07:42:42 : PreArm: GPS 1: Bad fix
09.03.2024 07:42:42 : PreArm: AHRS: Not healthy
09.03.2024 07:42:35 : GPS 1: detected as NMEA at 9600 baud
09.03.2024 07:42:22 : GPS 1: detected as NMEA at 9600 baud
09.03.2024 07:42:12 : PreArm: GPS 1: not healthy

MT3339 itself can do much more, but there is no config support in Ardupilot for writing configuraiton to NMEA-type GPS.

The easy way around was to order a holybro micro M10 which is roughly the same size.
We’ll see if that one does any better.

Again summing it up, NMEA-type GPS don’t work with Ardupilot, U-Blox is the de facto standard.

You can flash it to 5hz or 10hz firmware but I would recommend a ublox receiver.

the file names explain there properties
for example: AXN2.10_5013_3339_96.1151100.1

3339 = Model number.
96 = baud rate without the zeros (9600).
1 = 1 Hz.