Upgrading a clone 433MHz telemetry kit

I recently switched from an older PixHawk hardware to the PX2.1 (the Cube).

I reused a 433MHz telemetry kit changing the connector and it was working seamlessly until I inadvertently upgraded one of the two modules firmware, now the modules don’t seem to communicate anymore.
The main led is green solid, meaning there is a connection, but no matter how I change the parameters, the two radios don’t seem to communicate.
Now, the obvious solution is to upload the new firmware on the other module, however it lacks any connection interface. Is it possible to interface it with a pc via ftdi? Any connection schematic?
Thank you

look at this : about 1/2 way down:

The easier solution is to flash the ground radio back to V1.9. See these posts for the same problem and one solution: Or you can flash your Air radio to V2.0 via FTDI

Thanks it solved the problem.
For anyone in the same situation, simply interface the telemetry 4 cables (5V, GND, RX, TX) with the FTDI connector.