SAMD21: Unexpected port I/O failure mode [IDENTIFIED: ESD]

[ataradov]

Path does not matter, the signal normally does not go "through" TVS. TVS is just sitting on the line and clamps it to a set voltage in case of an over-voltage. It does so by passing the current through itself.

Clamping to both supply rails is better, but it is hard to tell if it is necessary here.

[nigelwright7557]

Usual problem with micros when ports dont work is port is set to analog.
I know on PIC's you have to set ANSEL register accordingly.