Question 1

What does NO (Normally Open) mean on an arcade button?

Accepted Answer

NO (Normally Open) is the switch terminal that is disconnected when the button is not pressed. When you press the button, it connects to the COM terminal, completing the circuit. Wire your GPIO signal wire to the NO terminal.

Question 2

What is active-low logic in arcade wiring?

Accepted Answer

Active-low logic means the GPIO pin normally reads HIGH (3.3V via pull-up resistor) and goes LOW (0V) when the button is pressed, shorting the pin to ground. This is the standard wiring scheme for all arcade GPIO inputs on Raspberry Pi.

Question 3

What is BCM numbering on Raspberry Pi GPIO?

Accepted Answer

BCM (Broadcom) numbering is the GPIO pin numbering system used in software configuration. BCM numbers like GPIO 17 differ from physical pin positions (pin 11). Always use BCM numbers in config files. Run 'pinout' in terminal to see the mapping.

Question 4

What is a daisy-chain ground in arcade wiring?

Accepted Answer

A daisy-chain ground is a single ground wire that connects from one button's COM terminal to the next, creating a chain. All buttons share one ground connection back to the Pi, reducing the number of wires needed from the GPIO header.

Question 5

What is a spade connector and why use it for arcade buttons?

Accepted Answer

A spade connector (also called quick-connect or 0.187" terminal) is a flat metal clip that slides onto a microswitch tab. It lets you connect and disconnect wires without soldering, making button swaps and troubleshooting easy.

Question 6

What is SPI and why does the 3.5" display need it?

Accepted Answer

SPI (Serial Peripheral Interface) is a high-speed communication protocol the Pi uses to talk to the 3.5" IPS display. It uses GPIO 10 (MOSI), GPIO 11 (SCLK), and GPIO 8 (CE0). Enable it via sudo raspi-config → Interface Options → SPI.

HARDWARE GLOSSARY