AVR Shift Register

A super simple example of using an 8-bit shift register with an ATTiny85.

Introduction

This program simply pushes 8 bits to a serial-in/parallel-out shift register. The output pins of the shift register are connected to LEDs. The program then makes a little dance with the LEDs, but mostly I made this just to learn how to use a shift register.

Ingredients

• ATTiny85
• SN74HC595 8-bit Shift Register
• Some LEDs & Resistors

Install

NOTE: The makefile uses avr-gcc and avrdude to compile and upload. It also assumes you're using a usbtiny programmer, like the Sparkfun Pocket AVR Programmer.

1. Connect your programmer

2. Compile and upload

   $ make upload
   

Schematic

Wiring Notes

• PIN 10 (SRCLR') on the shift register needs to go to VCC.
• PIN 13 (OE') on the shift register needs to go to GND.

Resources

• Datasheet for SN74HC595 shift register
• Sparkfun's page for the shift register
• Super useful description of how a shift register works, with graphs!
• Instructable with a really good makefile and code
• General info on ATTiny85 registers and ports
• Notes on connecting and programming the ATTiny85