I bought a caddx loris a few months ago.

Everything was working as expected: the VTX, the HD/4K recording...
Then I wanted to control the camera through its TX/RX pins... I suld wires on the pins then plug them to the flightcontroler UART and set it up with the runCam protocol.

So starts my troubles....

The camera seem now to be in a zombie mode....

When powering the camera (12V), only a violet LED in lit. Any action (clic, double clic, tripple clic, long clic, etc.) on the button, does nothing. Any action with the 5D pad does nothing. With or without the SD card, same behavior.   (even unplug the camera sensor does not change the behavior)
The only noticable change in the behavior: when powered with 5V, the led color is blue instead of violet (red+blue)

The documentation is quite inexistent with this device (or maybe I haven't search in the right place), the only documention talks about red light (red led off: camera off, red led solid: on, red led blinking: recording)... with only that, I cannot go very far in my investigations....

I double-checked my solderings, but there are no short-circuits, no (visible) interactions.

Does anyone know about where to find docs about this device or have some tips/tricks that I may try? (else than contacting the manufacturer for a new device )

Thanks!

Have you tried removing the TX/RX camera control UART wiring from the FC again to see if it still misbehaves with that wiring no longer connected?

Yes I've tried... the first thing I tried.
no much difference: with uart plugged, the board has no light, but le light comes with a small push on the onboard button.

I have a question: what is the voltage of the uart port? is it 5V?
if I unplug the uart, with a voltmeter, I measure 3V between GND & TX or between CNG & RX.... unfortunately I dont have osciloscope...

thanks

UARTs on the STM32 MCU's output a logic high signal as 3.3V and a logic low signal as 0V.

Yes, that's what I found.
Unfortunately I've plugged it to an Arduino, which operate in 5V...
I fear that my board has fried... (a small hope is that most devices have protection against high tension)

They could have written a warning!

We get no warnings on anything in this hobby unfortunately. We are lucky if we even get a manual and often have to scrabble around on the internet looking for wiring diagrams and information on things that others have already managed to work out for themselves.

Thanks... i will try again to communicate at 3.3v level... without much hope.
Then I think I will order a new board (I already see that they are selling sepparate parts)

Quick update on my issue.
I contacted the Caddx Support through their facebook group. 
They answered me quite quickly and responsively.

After the obvious questions and manipulations, they ask me to remove one diod from the board:

I've done that and.... no miracle, nothing change....

So they send me another DVR board, because they did not understand the issue.
They ensure me that the 5V level on the UART is not enough to fry the board.
To be honnest, I doubt of that affirmation, I will now only use 3.3V voltage level just in case....

Caddx has been very helpful with me. I crashed my Loris that I had mounted to the top plate of a drone. It wiped off the 2 buttons, and the wi-fi antenna. I ordered the wrong board. Caddx sent me the right board no charge! Good customer support!