LED Cube

This readme explains how to setup the development environment for the LED cube. Furthermore, it explains how to build and deploy binaries for the LED cube.

Inspiration

This project is based on and inspired by chr's LED Cube 8x8x8. I started this project when I was a university student learning electronics. The intent was to copy chr's work verbatim as I did not yet fully understand all the concepts.

As a busy student, it took around 4 years to complete the build. This is because I really only worked on it during school holidays. I learned a lot from this project. It flexed by my theoretical and practical knowledge of embedded programming and electronics.

Now, I hope to give back to the project by coming up with some interesting modifications and sharing them with the community.

Environment

The development environment is listed below. While the instructions are written for macOS, they should also easily be adaptable to Linux or (maybe) Windows.

• OS: macOS 11.1 20C69 x86_64
• Host: MacBookPro11,4
• Kernel: 20.2.0
• Shell: zsh 5.7.1
• Terminal: iTerm2

Hardware Modifications

Note that I have swapped out the atmega32 for a atmega324pa since I already have one from a previous project.

Prerequisites

Since I am developing on a mac, I will use homebrew to install the dependencies needed to compile the AVR firmware and load binaries.

Two things are needed:

• avr-gcc
• avrdude

The AVR GCC compiler is used to compile the firmware and avrdude is used as a flash programmer.

You should also have a working LED cube.

Compiling

The cube firmware is built using make, there is a makefile in the root directory. Some build goals are listed at the top of the file. Most common is:

    make all

To clean the generated object files:

    make clean

Flashing

avrdude is responsible for flashing the device. The ISP is the usbtiny by sparkfun.

To program the board using the USB tiny, run the following command:

    avrdude -c usbtiny -p m324pa -B 1 -U flash:w:Main.hex

You can also run the make goal

    make program

Test Program

There is a small program to test the LED cube in the test folder. It can be built with make and is useful for debugging dead LEDs or broken connections within the cube.

Hardware Design

In order to reduce the number of ICs and IOs needed by the LED cube, the latch board will be replaced by a CPLD. The CPLD selected was an Altera (now Intel) Max II device. It will serve as an IO expander and perform all the logic that the multiplexer board in the original design did.

Source and project files for the CPLD are found in the hdl folder. Since CPLD development is only supported under Linux, I used a VM. The VM is managed and provisioned using the following software

• VirtualBox
• Vagrant
• Ansible

Prerequisites

The following steps are needed to setup the host machine:

1. Install virtualbox
2. On macOS make sure to give proper permissions:

• settings > security & privacy > privacy > Accessibility
• settings > security & privacy > privacy > Input Monitoring

Note: when first installing virtualbox there will be a popup asking to give it permissions, this can be found at settings > security & privacy > general Make sure this succeeds, virtualbox will not work without it

1. Install vagrant using homebrew brew install --cask vagrant

Running VM

The VM can be accessed using the following commands:

1. vagrant up
2. vagrant ssh
3. (in VM terminal) sudo startx

• This starts the graphical environment

1. Quartus can be run by executing /opt/intelFPGA/quartus/bin/quartus

On the first run, vagrant up can take quite a long time. This is because Ansible is provisioning the machine. This includes installing quartus and all its dependencies. Special thanks to Embida, whose playbook I copied from to get started.

Why Vagrant?

USB support. Docker is a great tool for many projects, but on macOS hosts, Vagrant offers much more seamless USB support. USB is needed to control the USB Blaster that programs the CPLD.