I have an ESP8266 where I took one of the GPIO pins, configured the pullup on the input, then connected it to one lead of a 15m cable and the other lead to the ESP8266 ground.
The problem I have is that the input is flaky all the times, high/low. If I remove the leads to the cable, it's stable high. I measured the cable and with the leads connected together to one another, there's is a resistance of a 1.03 ohm. If the leads are not connected as they are 99.9% of the time, there is no resistance on the cable.
What am I doing wrong? How can I fix this issue?