Some compatibility issues with u-blox NEO-M9N GPS

anbello · August 21, 2020, 5:05pm

I am testing this GPS that use this u-blox 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.

Here the log:
https://drive.google.com/file/d/17pOy13ih4HvFz3kv3uj_pgOPlL2dC7gO/view?usp=sharing

vosair · August 21, 2020, 5:16pm

Interesting. I’ve been using the mRo m9n module without any issues, so it definitely can work. I’ll have to look at my logs and see if anything pops up.

anbello · August 22, 2020, 6:00am

The mRo module is connected via CAN port the Drotek one via Serial port, maybe this cause the strange behaviour of my module.

anbello · August 22, 2020, 12:51pm

The problem should be here

github.com

ArduPilot/ardupilot/blob/master/libraries/AP_GPS/AP_GPS_UBLOX.cpp#L1181


    _have_version = true;
    strncpy(_version.hwVersion, _buffer.mon_ver.hwVersion, sizeof(_version.hwVersion));
    strncpy(_version.swVersion, _buffer.mon_ver.swVersion, sizeof(_version.swVersion));
    GCS_SEND_TEXT(MAV_SEVERITY_INFO, 
                                     "u-blox %d HW: %s SW: %s",
                                     state.instance + 1,
                                     _version.hwVersion,
                                     _version.swVersion);
    // check for F9. The F9 does not respond to SVINFO, so we need to use MON_VER
    // for hardware generation
    if (strncmp(_version.hwVersion, "00190000", 8) == 0) {
        if (_hardware_generation != UBLOX_F9) {
            // need to ensure time mode is correctly setup on F9
            _unconfigured_messages |= CONFIG_TMODE_MODE;
        }
        _hardware_generation = UBLOX_F9;
    }
    break;
default:
    unexpected_message();
}

F9 and M9 have the same hwVersion, Ardupilot try to config the M9 as an F9 and fails.

If I comment line from 1182 to 1185 and change 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.

anbello · August 25, 2020, 6:43am

I opened an issues about that:

Tulle · October 6, 2020, 4:25pm

I have the same issue, commented out the version check and forced it to M8.
Now I get 25+ satellites. Will there be a fix for this?

Christian81 · October 17, 2020, 7:21pm

Does the problem still exist? We tested it a while back, worked great, but always to disable the gps check, which is not an ideal solution.