Meshtastic

T-Beam GPS problems (hardware)

Support
#1

Hi… I’m sorry if this is not directly related to Meshtastic, but is a bit more related to general hardware.

I bought a ttgo t-beam and i think the gps module might be broken. I cant get any GPS data in any application, or any of the test programs or the serial pass through. I haven’t been able to get any indication that the GPS module is active at all via the serial interface.

The board version is a T22-V1.0 20190612 with a Neo-6M GPS. I’m aware that it requires the correct setup of the power management chip to enable GPS.

I also read that in some cases, the GPS chip will only work reliably at a reduced baud rate (4800), but no deal.

I tried quite a bit of fiddling with settings, pins, addresses and speeds at this point.
i’m aware that there is both https://github.com/LilyGO/TTGO-T-Beam (with an updated program for this board version) and https://github.com/Xinyuan-LilyGO/LilyGO-T-Beam.

Any ideas how i can verify that the GPS chip is … well, even reachable at this point?

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#2

I bet your problem is that the GPS is not powered. On the TBEAM there is a PMU (power management unit chip) called an AXP192. You need to tell that chip to turn on power to the GPS. If you look at meshtastic-device/src/main.cpp you’ll see an example you can copy. If you do that you can then set the TBEAM outside for 15 mins or so and the red led will start flashing (even if you never talk to the GPS). That tells you the GPS started and found satellites.

The default baud rate is 9600 bps and you should leave it at that.

#3

And also confirm you loaded the correct firmware version that relates to the TBeam.

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#4

Thanks for the answers.
I’m aware of the PMU and have already tried multiple different examples to enable the GPS chip without success.
Guess i’ll have to keep looking.

#5

I bought two T-Beam modules, both T22_V1.1 20191212 version, and one of them also appears to have a bad GPS module. The other works fine, so it could just be bad luck…

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#6

@dafeman has a good point. Even though you aren’t normally using our code. You might try installing one of our prebuilt bins (per our README). Then you could at least know if your hardware is fine (set it outside and the red led should blink)

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#7

heh, well, that was the first thing i tried of course. I have gotten the red LED to blink on some occasions.
I’m pretty sure now that my boards serial connection is somehow faulty.
Thanks again for the replies :wink:

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