Simple tool for reading a resistor with Arduino.
Make a voltage divider with: R1 100 Ohm Vout on A0 R1 1000 Ohm Vout on A1 R1 10000 Ohm Vout on A2 R1 100000 Ohm Vout on A3
Serial Output will show the resistance and tolerance of the resistor. No need for knowing the colour codes.
Put a unknow resistor (R2) between R1_OUT and Ground
I made this code for fast sorting out all my loose resistors after prototyping on a breadboard.