As a network engineer, I never go anywhere without my Ethernet cable tester. That and a audible cable finder (fox & hound) are invaluable for finding and testing cable pairs. Today I’m showcasing a Arduino Ethernet cable tester. This tester is switchable for a straight through or crossover test. Test results are seen in a ordered line of LED’s, as well as serial output that could be displayed on a LCD and written to a sd card.
A Arduino fox and hound will come later, and then maybe a TDR distance to fault tester. We will see.
https://variecose.wordpress.com/2012/04/15/ethernet-lan-rj45-cable-tester-with-arduino/