Hardware & IoTLesson 101Free preview

RasPi LED & Pushbutton

This lesson is part of Node.js · All levels

Summary

This lesson combines the output and input of GPIO: LEDs that light up when a button is pressed on a Raspberry Pi. You'll configure one pin as input and one pin as output, and then react to a change in value via event watch. It's the foundation of the interactive hardware interface.

Key points

One pin set 'in' for the button (with the pull-down resistor) and one pin set 'out' for the LED.
Use pin.watch(callback) to react when the button is pressed or removed.
Debounce is required because the contact button can bounce.
Read the pin value with pin.readSync() when you need to check for up-to-date status.
Make sure the voltage and resistor are as specified by Pi (3.3 V, not 5 V on the input pin).

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