I have noticed a discrepancy between the datasheet of the ESP8266EX (version 4.4) and my measurements.
According to the datasheet input leakage current should be 50nA yet I'm measuring 25uA.
That's a factor 500x difference and has a big effect on big resistor values;
50nA running through a 1MOhm creates a voltage drop of 50mV
25uA running through a 1MOhm creates a voltage drop of .. 25V (if it were an ideal current source)
My measuring setup:
ESP-WROOM-02 running nodemcu on pcb with GPIO14 and 3.3V line hooked up to a uCurrent.
uCurrent hooked up to cheap, non-calibrated(!) DMM
Code running on ESP - "gpio.mode(5, gpio.INPUT)"
I've also noticed a voltage drop of ~1.5V when connecting GPIO14 to 3v3 through a 500K resistor while measuring with a Hantek DSO5102B (also not calibrated unfortunately)
Can someone confirm this behaviour?