Is it possible to limit maximal negotiated GPS serial bitrate? Tbeacon stopped working after upgrading to plane 4.2

I’m using tbeacon module (great lost model finder device) on all my FPV planes but after upgrading from 4.0.9 to 4.2.1 it stopped working.
Tbeacon is passively listening to the data from the GPS module to the FC, parsing them internally and in case of a crash can spell them in the voice to an UHF radio.
It can autodetect wide range bitrates and protocols and so far worked with any autopilot and version I used.
I suppose that bitrate or protocol negotiated between FC and GPS had changed between from 4.2 and tbeacon can’t parse the new protocol or speed.
Is there a chance to force previous protocol and serial speed on 4.2 to keep my tbeacons working?
At the moment it’s for me no go for upgrading :frowning:
Omnibus F4V3 running 4.2.1, BN-220 GPS, tbeacon 0.58

I checked what protocol and bitrates were negotiated for each version and for 4.0.9 it was ublox @ 115200 while at 4.2.1 it’s ublox at 230400. I’m afraid that tbeacon by harware limits can’t read 230k serial.
Is it possible to limit maximal negotiated GPS serial speed to 115k?

You can disable GPS autoconfiguration and manually set your GPS parameters.

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Have the same problem. Do you solve it?

Yes, it helped!
I let FC to configure GPS and save config to it with AP 4.0.9, then disconnected GPS, upgraded AP to 4.2.2, disabled autoconfig and reconnected GPS.
So far it works, GPS keeps communicating at 115k and tbeacon works.
I only hope that GPS settings are stored in an eeprom and not just in battery backed RAM where they can get lost after some time. I’ll see after a longer period of unuse - now I fly almost daily :slight_smile:
@developers: could you introduce a new parameter something like GPS_MAX_SERIAL_SPEED to solve it clean way?
Thanks! Roman

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you should be able to use Ublox Ucentre software to manually change the settings if you can connect the gps to a usb serial adapter.

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GPS_DRV_OPTIONS=4 was added to solve your problem some time ago.


You are right, but it’s a lot of different settings, not only serial speed so I hoped AP 4.0.9 did set all to the optimal values and I can just use them.
Persistence of the settings depends on the type of GPS - some don’t have eeprom. I think introducing the parameter to limit max. speed would be technically cleanest solution. AP would be then able to set all remaining parameters according as it needs.

Yes, thanks, I’ll test it - GPS_DRV_OPTIONS
looks like what I was looking for!

GPS_DRV_OPTIONS: driver options

Note: This parameter is for advanced users

Additional backend specific options

0 Use UART2 for moving baseline on ublox
1 Use base station for GPS yaw on SBF
2 Use baudrate 115200
3 Use dedicated CAN port b/w GPSes for moving baseline
4 Use ellipsoid height instead of AMSL for uBlox driver

I tested to set GPS_DRV_OPTIONS to Use baudrate 115200, but my FC keeps setting GPS serial speed to 230400.
I ticked in the mission planner bit with this name, which set value 4 (decimal) in the table and wrote settings.
I use Arduplane 4.2.2 on Matek 405 Wing and Beitian BN-880.
I set manually GPS to 115k and saved to the GPS, but after connecting to the AP and booting up it was reconfigured to 230k.
Did anyone tested if this option works on this version?
(Disabling GPS autoconfiguration works, but I think GPS_DRV_OPTIONS is a cleaner way to do it.)

GPS_DRV_OPTIONS = 4 seems not working at all!
I did another test with different board (Omnibus F4V3, different GPS ( VK2828U8G5FTTL) and Arduplane 4.2.3.
I connected brand new GPS module (default NMEA 9600) to the FC with already set GPS_DRV_OPTIONS = 4.
At boot it wrote In messages: GPS 1: detected as u-blox at 230400 baud and GPS is running at 230k.
Can someone please check and confirm that? If confirmed, I think it’s probably a bug.
Thank you