Secondary GPS doesn't works

[rligocki]

Describe the bug
On 1.9.1 stable I tried to connect two HERE2 GPS modules because of redundancy. GPS modules were connected to GPS1 and GPS2 ports on Pixhawk 2.1. Then I run GPS driver using command: "gps start -d /dev/ttyS3 -e /dev/ttyS4". The first GPS works ok, secondary GPS has no response

To Reproduce
Steps to reproduce the behavior:

1. Pixhawk 2.1 with stable 1.9.1
2. console command "gps stop"
3. console command "gps start -d /dev/ttyS3 -e /dev/ttyS4".
4. console command "gps status"

Expected behavior
There should be two sources of GPS.

Log Files and Screenshots

Additional context
I also tried different UARTs (/dev/ttyS1, ttyS2, ttyS6). At screenshot you can see ttyS6.

[julianoes]

Have you seen this docs? https://docs.px4.io/en/peripherals/serial_configuration.html

[rligocki]

Yep, I read it a few times. It does not work. I found that in default.cmake of FMU3 is GPS2 label missing.

SERIAL_PORTS
GPS1:/dev/ttyS3
GPS2:/dev/ttyS4
TEL1:/dev/ttyS1
TEL2:/dev/ttyS2
#TEL4:/dev/ttyS6

I added GPS2 label, now it starts after configuration of GPS2 interface. No need to use console.

[julianoes]

Could you point me to where in the code this is missing? Thanks.

[rligocki]

./px4rootFolder/boards/px4/fmu-v3/default.cmake. This file is missing label for GPS2 connector, but a setup for secondary GPS should work with TEL2 port. The problem still remains. I also tried to change primary and secondary GPS, but still, secondary GPS does not communicate with pixhawk.

[julianoes]

@dagar do you understand this?

[rligocki]

Update: Problem is somewhere in pixhawk2.1 and here 2 GPS module. I tried same start command of GPS driver and it worked with pixhawk 2.4.8 and Ublox M8N GPS modules. I thought that cable is damaged, but unfortunately, cable looks ok. Also checked that GPS is in I2C mode.