Arduino Mega2560 and expander MCP23017

[noiasca]

A Mega should be able to test 27 cables with the discrete pins.

some years ago I have written a short POC.
It tests each cable if it is connected to another cable:

Adruino Mega oder Due als Kabeltester

DrDiettrich: Das setzt voraus, challenge akzeptiert. Ganz was einfaches als proof of concept: /*   simple check of connections between defined test pins.   external pulldown resistor 6K8   by noiasca   https://forum.arduino.cc/index.php?topic=666835.0 */ const byte testPin[] {5, 6, 7, 8, 9, 10, 11, 12}; void setup() {   Serial.begin(115200);   Serial.println(F("\nCabletester"));   for (auto &i : testPin)     pinMode(i, INPUT); } void loop() {   check(); } void check() {   Serial.prin…