Heltec T114 generic GPS crash

[Dooomenik]

Hi all,

i have a Heltec T114 2.0 Node, firmware 2.5.20.4c97351 and a RUSHFPV Mini GNSS Module.
First i had trouble to get the GNSS module running. The redefine GPS RX and TX Pin don't seem to work.
I tried GPIO7/8, GPIO 28/30 and also GPIO9/10 which are the UART1_RX/TX pins. I connected GPS TX to Node RX and vise versa and set the redefine pins in the config. After that i also switched the connections RX/TX or after that the config (RX/TX switch) with no luck.
Other Position config were:
-Smart position enabled

• Use fixed position OFF
• GPS mode ENABLED
• And the redefine Pins in different variations

I ended up soldering the RX and TX to the GPIO37/39 pins of the boards GNSS connector with redefine pins at 0 (default).
Since that my GPS was working and it displays no sats and no gps lock
BUT
after a few seconds the whole Node resets all the time. It seems to be an issue with the GPS HARDSLEEP.
It alway crashes after this.

[36m←[0m ←[34m DEBUG ←[0m| 20:37:23 32 [GPS] ←[34m NMEA GPS time 2025-03-05 20:37:36 age 0←[0m
←[36m←[0m ←[34m DEBUG ←[0m| 20:37:23 32 [GPS] ←[34m Upgrade time to quality GPS←[0m
←[36m←[0m ←[34m DEBUG ←[0m| 20:37:36 32 [GPS] ←[34m hasValidLocation RISING EDGE←[0m
←[36m←[0m ←[34m DEBUG ←[0m| 20:37:36 32 [GPS] ←[34m Took 25s to get lock←[0m
←[36m←[0m ←[34m DEBUG ←[0m| 20:37:36 32 [GPS] ←[34m Predict 0s to get next lock←[0m
←[36m←[0m ←[34m DEBUG ←[0m| 20:37:36 32 [GPS] ←[34m 119s until next search←[0m
←[36m←[0m ←[34m DEBUG ←[0m| 20:37:36 32 [GPS] ←[34m gps_update_interval >= 0s needed to justify hardsleep←[0m
←[37m←[0m ←[32m INFO ←[0m| 20:37:36 32 [GPS] ←[32m GPS power state move from ACTIVE to HARDSLEEP←[0m
WARNING file:stream_interface.py __reader line:207 Meshtastic serial port disconnected, disconnecting... ClearCommError failed (PermissionError(13, 'Das Gerät erkennt den Befehl nicht.', None, 22))

Is there a way to disable the hardsleep?

BR, Domi

[Dooomenik]

My fault. Runs on 5V without level converter.

[hcker2000]

What did you do to fix this? I'm having the same issue.

[Dooomenik]

Hi, i thought the problem was, that the GPS (HGLRC M100 Mini) runs with 5V. But i get it working with a Heltec T190 without problems. Including the possibility to switch it via a 2N7000 Mosfet (don't forget an up to 100k resistor on the gate to avoid the reboot loop).

But yet no luck with the Heltec T114. It seems the relocation of the GPS TX/RX pins don't work.
It detects the GPS only on the TX/RX pins of the GPS connector but as soon as the GPS gets a lock, the T114 starts a continuous reboot loop.

[Dooomenik]

Update that was version 2.5.20. Same behavior with 2.6.4.

[heyitsyang]

I had similar symptoms. GPS would get a lock and would stop sending data. However, setting the GPS Update Interval to a more frequent value addressed the problem for me. Other GPS modules I have used just constantly spew, so meshtastic must sleep the module.

[heyitsyang]

One more thing to add, there appears to be a PCB layout bug on the Heltec T114. The pinout map shows that GPIO37 (TX_GPS) appears on the 8-pin connecter and as a through-hole pad on the PCB. However, examining the schematic shows that these two points labeled GPIO37 are not connected.

GPIO37 on the PCB is attached to chip pin P0.05 and GPIO37 on the 8-pin connector is attached to chip pin P1.05.