Ahh − Nice one Berni! So the ESD diodes provide a path from IO pin to VCC and they aren't rated for that continuous current. I want to have all of those lines open, and I haven't switched the ZED-F9P VCC, but perhaps I should... In any case, I will get some HEF4066BT,653 and put all my lines through them.
About the project, nothing really innovative - just working on a GPS product for the agriculture sector.
Talking about TVS, it's funny because I planned a PCB with unidirectional TVS on the RS232 lines, and was wondering why I was getting garbled output. And recently I bought and soldered a 200kHz oscilliscope from AliE (e.g.
https://www.aliexpress.com/item/32878694776.html), and the penny dropped...
