LEDs do not work as diodes in a keyboard matrixSix "diodes" tested
- BYV10-40 Schottky
- 1N34A Germanium
- 1N4001 Silicon
- 1N4148 Silicon
- Red LED 1.8mm
- White LED 2x3x4mm
When a switch is pressed that column (data pin) is pulled to ground through the diode and should read as low. When no switch is pressed that column remains in a high state, pulled to Vcc through a built in resistor. The 4 rectifying diodes all pull the voltage down to below 0.9volts. The two LEDs do not.
Testing was done using a 6 key macropad wired in a 2x3 matrix. This was connected to an Arduino Pro Micro running QMK firmware.
These graphs show the voltage drop when pressing the key of a particular diode. The major divisions are 2 volts.