RPi Tutorial EGHS:Shift Registers

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GPIO Hardware & Software Tutorials:

This page is part of a work in progress.


While most of these circuits may interface directly to the RPi, the use of a buffered interface (such as the one supplied by the Gertboard) is recommended which will help protect against damage. Alternatively, experiment with one of the Alternative Test Platforms.

Extreme caution should be exercised when interfacing hardware at a low level, you may damage your RPi, your equipment and potentially yourself and others. Doing so is at your own risk!


Considering the following site, Arduino - Parallel to Serial Shifting-In with a CD4021BE contains all the required information, there is little need to repeat it all here.

Unfortunately, it appears that the CD4021 does not work with 3.3V logic so an alternative chip should be used.

Rather than focus on the circuits, this guide will examine the software for application on the RPi.

Until RPi devices are available, I can not confirm this will work on a real RPi.
For now, I shall be using the TI LaunchPad (see  Alternative Test Platforms
for details) to test the hardware on (as it is cheap and the logic levels similar).

The Hardware



The Software

While the RPi is not available, I can only confirm the TI LaunchPad code works for me.

TI LaunchPad

Sample test code for shift register input (tested on TI MSP430G2553 device).