↓Skip to main content

Hypriot, wiringPI and a Blinking Light

·2 mins

The nice thing about a Raspberry Pi is the ease on how to control real hardware with it.

Kids in our days have it so easy to tinker with electronics, I wish it would have been that easy in my times. Those twenty years ago when I was tinkering around with resistors and capacitors there were no Arduinos, Rasperry PIs and all those wonderful toys.

In this and this post I have made a Docker host out of a Raspberry PI. It had one container running a web server with a single page.

The next step I took was to “talk” to the input and output pins and make a blinking LED “application” as kind of an “Hello World” example.

There is already an image that we can use for this purpose. It has a tool installed called wiringPI that we will use to turn an LED on and off.

I needed four steps:

  1. Create the docker-compose.yml that describes my “services”.
  2. Write a shell script for calling wiringPI to get this LED blinking.
  3. Getting the Raspberry to start everything after bootup.
  4. Wire-up the hardware.

The docker-compose file looks like this:

{% gist 20ed411159fc04999c06 docker-compose.yml %}

For actually setting the output mode of the port and letting the LED blink I have created this shell script:

{% gist 20ed411159fc04999c06 blink.sh %}

I have put everything on Github. So, while having logged into hypriot you only need to

git clone https://github.com/twissmueller/docker-pi.git
cd docker-pi
git checkout tags/2015-12-01

For step three the following line needs to be added to /etc/rc.local:

docker-compose -f /root/docker-pi/docker-compose.yml up -d

Assuming that the all the stuff is in directory /root/docker-pi.

Now it’s time for some wiring to do. There is a wonderful tool called Fritzing for designing, illustrating and sharing your Raspberry (not only) projects.

Blinking LED Setup

You can download the Fritzing project from this link.

Done for today!