SoftRF MB174 on T-Beam with U8 GPS vs. Skydemon

[Andreas Titze]

Dear group,

I'm currently struggling to connect my T-Beam (w/Ublox8 and MB174) to my Skydemon (on multiple Galaxy Android devices w/Android 11 and 16) via BTLE.

Skydemon connects easily to Stratux via BTLE but hangs on my T-Beam at "Seeking Satellites".

I did a comparison of the relevant GPS Messages sent by Stratux vs. sent by T-Beam.

the only notable difference is the DOP values in $GPGSA. Per definition they are expected to be in the x.x format with only one decimal figure. Sent by SoftRF from T-Beam is a x.xx value.

Looks like Skydemon is struggling to decode that message. Hence not accepting the fix.

Is there any way to change that behavior? I reckon it must lie somewhere in the Ublox 8 init sequence.

Any help appreciated.

Best regards

Andreas

[Moshe Braner]

If SkyDemon cannot interpret the sentences due to an extra digit then I would say that's a bug in SkyDemon, and perhaps you should tell them about it.  But meanwhile, can try (via the U-Center software from uBlox) the UBX commands in the CFG-NMEA section, which allow a "compatibility mode" with older versions.  Although it only mentions it affects digits in the lat/lon, not the DOP.

[Andreas Titze]

Hi Moshe,

just solved the mystical problem.

Stefan helped me out with his settings.txt file and that brought clarity. 

I did activate the  "gn_to_gp setting" (ment for robustness) and that broke it. 

Could it be, that You do not recalculate the checksum after the change of "GN" intro "GP"?

That said, now I'm back to the known behavior. T_Beam connects nicely to Skydemon under Android via BTLE. 

Only the latest Android versions (namely 15 and 16) have a problem.

Thanks for looking into it!

Andreas

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[Moshe Braner]

Hi Andreas. You are correct, I need to re-calc the checksum after patching the "GN" to make it "GP", if that setting is used.  I'll fix that in the next release.  Thanks for reporting.