NOTE - this is the previous version of the installation part of https://appliedgo.net/digispark.

This is outdated information that only serves documentation purposes.

Controlling a Digispark board from Go code

With a few more (software) ingredients, the I/O ports can be controlled from Go code running on a PC/Mac/LinuxBox/etc. These are:

  • LittleWire
  • The micronucleus cli app
  • Gobot

LittleWire is basically a script that adds USB communication capabilities to the Digispark. With an accompanying library at the USB host’s end, the board’s I/O ports can be remote-controlled from an app running on the host.

micronucleus is a bootloader that comes preinstalled with Digisparks. (It needs a little space in the microcontroller’s flash memory, leaving about 6KB memory available for scripts.) It has a companion CLI app that is needed for installing LittleWire on the device.

Gobot is a Go robotics framework that connects Go apps to a large array of electronic devices, from the little Digispark to Arduino, Raspberry Pi, and even Quadrocopters.

And here is how I used all this to make the onboard status LED blink, and a servo motor move.

The steps

Step 1: Install the micronucleus CLI app

I compiled the micronucleus CLI tool from its source in two steps:

Clone the source

A simple git clone fetches the source code from GitHub:

git clone https://github.com/micronucleus/micronucleus

Compile the command

After this, I cd’ed into micronucleus/commandline and ran make:

commandline $ make
Building library: micronucleus_lib...
gcc -I/usr/local/Cellar/libusb-compat/0.1.5_1/include -L/usr/local/Cellar/libusb-compat/0.1.5_1/lib -lusb -Ilibrary -O -g -D MAC_OS -c library/micronucleus_lib.c

On my Mac, I got a couple of warnings but as the micronucleus command turned out to work fine, I consider these warnings as benign. On my Lubuntu netbook, make finished without any warnings.

Step 2: Install LittleWire

Again, only two steps are required.

Download littlewire_13.hex

The “firmware” script LittleWire is available at the LittleWire download page

Install LittleWire on the device

Then I ran micronucleus:

commandline $  ./micronucleus --run ../../LittleWire/littlewire_v13.hex

(I had LittleWire in a directory next to the Git workspace of micronucleus; if you want to repeat these steps, adapt the path as needed.)

micronucleus then asked to plug in the device into an USB port. (The Digispark, when powered on, listens on the USB port for some seconds, and if the host does not send anything, the device disables the USB port, because two of the I/O pins have a double use as USB channels, and disabling the USB port makes these two ports available for hardware wired to the board. This is why the board must be plugged in only when the host app is ready.)

I plugged in the board, and micronucleus uploaded the LittleWire firmware in a few seconds.

Step 3: Install Gobot

For this, I simply followed the instructions from the Gobot documentation.

For Mac and Linux, some USB libraries need to be installed. On the Mac, this is a one-liner if you have Homebrew installed.

brew install libusb && brew install libusb-compat

On Ubuntu (and surely also on other Debian-based distributions), a simple apt-get does the trick.

sudo apt-get install libusb-dev

Now I was ready to fetch Gobot and install the Digispark platform package. (If you are new to Go: the ellipsis at the end of the go get line advise the go get tool to also download all subprojects, even if the top project does not import them. The -d is also important as this prevents the go get tool from installing anything at this point. The only thing we want to install is the Digispark package.)

  go get -d -u gobot.io/x/gobot/...

The next step installs the digispark library. I first ran into an error (“undefined: lw”) until I realized that I had cgo disabled. On a Bash shell, the prefix CGO_ENABLED=1 ensures that go install uses cgo.

  CGO_ENABLED=1 go install gobot.io/x/gobot/platforms/digispark

While this worked on the Mac, on Linux I got a “package libusb was not found” error message. Apparently the error was raised by a tool named pkg-config. I wasn’t able to figure out the reason for this, so my Linux-based test ended here.

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