I hope you don't mind me asking about this, I know there are other threads, and I did read through them, but I want to be sure I understand.
I have a UART open to the "outside world" (usually those cheap USB-UART cables from aliexpress). They run at 3.3V, and will feed this 3.3V to RX (and some to TX) when my board is shut down.
Currently I have 1k resistors in series with TX and RX, to limit current, but perhaps that won't be quite enough. It shows around 1V on the pins (when shut down), which is over the 0.5V limit. 4.7k might be better as long as it doesn't interfere with bit rate (57600). The internal diodes are supposedly good to 1mA, so 4.7k qualifies, but 1k does not.
I haven't added any caps yet (from uart pins to gnd), should I?
Should I bother with a regular or TVS diodes as well, for fear of esd? Or is the 4.7k enough protection?
As usual: "What else do people normally do"? I think protecting against 3.3V applied to these pins (maybe 5V) and ESD when the system is off would be sufficient.