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cfr34k / t-echo-lora-aprs

LoRa-APRS firmware for the Lilygo T-Echo
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No GNSS satellite status displayed on some devices #4

Closed cfr34k closed 1 year ago

cfr34k commented 1 year ago

Some devices do not show the currently in-use, tracked and in-view GNSS satellites. Location, altitude, course and speed seem to work though, as the tracker works normally.

The main symptom is that if GNSS warmup or the tracker are enabled, the GNSS status field in the status line at the top of the display becomes black (GNSS fixed), but satellite counts stay at “0/0/0”.

This is probably a problem in the parser for the relevant NMEA sentences.

Unfortunately, I don't have such a device available, so I can't debug this at this time.

cfr34k commented 1 year ago

I recently had the opportunity to look at the UART signal of a device with this problem. It turns out that this device only sends the GNGGA and GNRMC sentences, so somehow the GNSS module is misconfigured.

cfr34k commented 1 year ago

After some research and unsuccessful tries to reconfigure the module using MTK sentences it turns out that the module does not listen to MTK at all, even though that’s the documented version! :roll_eyes:

It actually can be configured using the CASIC protocol which has features very similar to MTK. Thanks to Meshtastic for turning this up!

Therefore, I now send the PCAS03 message to enable the necessary NMEA sentences. I hope this works. It will be released with v0.7.

cfr34k commented 1 year ago

Version 0.7 containing the fix has been released. I'm leaving this issue open for another two weeks and will close it if nobody complains in that time :)