Electron - Permanent damage to serial pins

I am in the process of integrating a TTL serial camera with the electron (Chinese brand bur seems to be good quality).
After a few moments of connecting the camera to the serial port (serial 4) the electron stared behaving abnormally and the serial port stopped functioning. It would restart very minute or so.
After disconnecting everything I checked continuity between pins C2 and C3 to find out that they were internally SHORTED. What is even worse is that they were also shorted with 3v3 and ground pins of the electron.

I then checked the camera, the maximum voltage on the rx tx pins was 3.3v. never went above that.
Repeated the same experiment with serial 5. It was working initially (tested using echo via serial 1) then as soon as I connected the camera, I lost that port too. Now serial 5 behaves the same way and the electron itself restarts randomly.

Since then I am using a Max3232 to convert TTL fro camera ->RS232 and back to TTL (idea was to protect the pins on my new electron) and its been working fine.
Was using a TTL N-MOSFET to control gnd signal to the camera via the electron (I would like the ability to power down the camera when not in use)
Any idea on whats going on here.
Also, is thee a better way to protect the rx tx pins on the electron.

Hello! did you ever figure out how to protect the pins and what was happening?

What N-mosfet where you using?


It’s been a while.
I remember adding additional protection on the RX TX pins and we didn’t have any issues.