I have an FTDI cable here, and I have no idea if it’s 3V TTL or 5V. I want to be sure that plugging it into my TX2 won’t fry something. Will the RX / TX pins on the TX2 accept a 5V signal?
The port is 3.3V (“TTL level”). I don’t know if 5V would hurt it, but it would certainly be the wrong value (which means it may not be reliable even if it doesn’t do damage). Imagine that when your UART receives 3.3V but considers 5V as “high”…it is questionable whether things would work as expected.
The ports seem to have some ESD protection through the 1.8V → 3.3V level shifters (as the Jetson itself is 1.8V)
5V would hurt it, if not immediately, then over time. The easiest way to translate the level is to add a 1 kOhm resistor followed by a 3.3V zener to ground. This will draw about 1.5 mA continuously though.
A better translation uses something like an NTS0101.