- Learn to solder
- Basics: diodes
- Socketing is worthwhile if using pro micros
- Simplify soldering headers
- test that a keycode is pressed
A diode prevents current from flowing backwards, basically making the circuit a 'one-way street'.
Most DIY keyboards use diodes. There are two types, through-hole (also abbreviated as THT) and surface mount (also abbreviated as SMD). Through-hole is more common.
Diodes have polarity, meaning that they have a specific direction they must be soldered in to function properly. This polarity is usually also printed on the PCB. The symbol for diodes usually looks like this ▶❙, a triangle with a bar across the point. The diodes themselves also usually have a stripe printed or etched on them. The orientation of the lines should match when soldered.
Diodes are not sensitive to heat.
There are many good websites to use to test keypresses, such as Keyboard Tester.
Keep in mind that firmwares like QMK sometimes use non-standard/custom keycodes that cannot be detected. It may be worth using a standard keycode at that switch position for testing purposes.