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Raspberry Pi 3 Cookbook for Python Programmers - Third Edition
book

Raspberry Pi 3 Cookbook for Python Programmers - Third Edition

by Steven Lawrence Fernandes, Tim Cox
April 2018
Beginner content levelBeginner
552 pages
13h 58m
English
Packt Publishing
Content preview from Raspberry Pi 3 Cookbook for Python Programmers - Third Edition

Hardware multiplexing

An LED requires a high voltage on the anode side and a lower voltage on the cathode side in order to light up. The RGB LEDs used in the circuit are common cathodes, so we must apply a high voltage (3V3) on the RGB pins and a low voltage (0V) on the cathode pin (wired to pins 1 to 5 for each of the LEDs).

The cathode and RGB pin states are as follows:

Cathode and RGB pin states

Therefore, we can enable one or more of the RGB pins, but still control which of the LEDs are lit. We enable the pins of the LEDs we want to light up and disable the ones we don't. This allows us to use far fewer pins than we would need to control ...

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Publisher Resources

ISBN: 9781788629874Supplemental Content