Pix32v5 - issue with activating serial 4, 5 & 6 (telemetry 4 & 5)

Hi,

I’m using the Holybro Pix32v5 in combination with the Base Mini.
I need additional MavLink-communication (OSD, Receiver), using telemetry 3 (serial 4) & telemetry 4 (serial 5).

What I did:
In Ardupilot, serial 4 & 5 are configured as MavLink (2), but there is still no communication.

Checks done:
I checked the wiring on serials 4 & 5: this is correct (Rx & Tx).
I swapped the connectors from serials 4 & 5 with serial1 & serial 2 (telemetry 1 & 2): MavLink-communication works.

Based on the documentation I found, serials 4, 5 ,& 6 are disabled by default.
How can I activate serial 4 & 5 to use MavLink?

Holybro_Pix32-V5-Base-Mini-Pinouts.pdf (397.8 KB)

Did you set the baud rates?

Yes. Baud rate is 57.