GPs Glitches Help me understand them

anbello · August 24, 2020, 7:36pm

Hi Patrik, I am testing the m9n:

[Edit]
I raised an issue:

github.com/ArduPilot/ardupilot

AP_GPS: compatibility issue with u-blox NEO-M9N GPS

opened 08:26AM - 23 Aug 20 UTC

closed 07:17AM - 06 Nov 20 UTC

anbello

## Bug report **Issue details** I am testing this [GPS](https://store-drot…ek.com/917-DP0801.html) that use this u-blox [module](https://www.u-blox.com/en/product/neo-m9n-module) (NEO-M9N) with Pixracer and ArduCopter V4.1.0-dev. It is recognized and I see this msgs: ``` [MAV 001:1] GPS 1: detected as u-blox at 230400 baud [MAV 001:1] EKF3 waiting for GPS config data [MAV 001:1] u-blox 1 HW: 00190000 SW: EXT CORE 4.03 (6c5018) ``` But the configuration is not saved even with GPS_SAVE_CFG=1 and I have the following repeated msgs: ``` PreArm: GPS 1 failing configuration checks GPS 1: u-blox solution rate configuration 0x10008 ``` I cannot takeoff in LOITER but I was able to take off in ALTHOLD and then switch in LOITER with success. The number of seen GPS was 16, that I think is low for this kind of GPS but it could be related to unsuccessful configuration. **The problem should be here** https://github.com/ArduPilot/ardupilot/blob/master/libraries/AP_GPS/AP_GPS_UBLOX.cpp#L1181 F9 and M9 have the same `hwVersion`, Ardupilot try to config the M9 as an F9 and fails. If I comment lines from 1182 to 1185 and change line 1186 in: `_hardware_generation = UBLOX_M8;` the M9 is configured as an M8, the configuration succeeds and it is saved. Obviously this is not a fix, it serves only to point were the problem should be. **Version** ArduCopter V4.1.0-dev **Platform** [ ] All [ ] AntennaTracker [x] Copter [ ] Plane [ ] Rover [ ] Submarine **Airframe type** Quad X **Hardware type** Pixracer **Logs** https://drive.google.com/file/d/17pOy13ih4HvFz3kv3uj_pgOPlL2dC7gO/view?usp=sharing