I wish to experiment with GPIO line protection circuits in the form of Transistors, Zener and Schottky diodes with resistors.
What might be a simplistic 5v GPIO equivalent circuit to test if my protection experiments are clamping my test spikes. Would be nice if it drives a Led so I can see when failure has occurred.
I have a device that uses a PIC16F917. It has the traditional pull up to 5v and ground button to toggle the units activity. Because this input is extended off the device with a push button. The cable is acting like an antenna and one in five device fail due to installation where the push button cable is extended. Sharing plastic trunking with other power cables.
Datasheet says the port/bit that I am interested in it is a TTL compatible input and CMOS output. Input current clamp is 20ma with 0v to Vdd I believe.