This example will get you up and running quickly with a multicontainer setup on balenaCloud. The application plots our devices' CPU temperature on the device URL and LCD screen which is piped over using websockets. The system is composed of a simple static site server, a websocket server and a proxy and GUI service. These 4 components are defined in our docker-compose.yml as services and are only given as much privilege as is needed.

To get this project up and running, you will first need to signup for a balenaCloud account here, create an application, and add a device. Have a look at our Getting Started guide if you need help.

Once you are set up with an account, you will need to clone this repo locally:

$ git clone https://github.com/balena-io-projects/multicontainer-demo-rpi3

Then add your application's remote repository to your local repository:

$ git remote add balena [email protected]:username/myapp.git

and push the code to the newly added remote:

$ git push balena master

It should take a few minutes for the code to push. While you wait, let's enable device URLs so we can see the server outside of our local network. This option can be found in the Actions drop down in your device dashboard.

Give the GPU some more memory to run the GUI.

BALENA_HOST_CONFIG_gpu_mem=192

Device Configuration for PiTFT screens:

If you are using one of the piTFT screens, you will need to apply the following config.

BALENA_HOST_CONFIG_dtoverlay=pitft28-resistive,rotate=90,speed=62000000,fps=60
BALENA_HOST_CONFIG_hdmi_force_hotplug	1
BALENA_HOST_CONFIG_hdmi_group	2
BALENA_HOST_CONFIG_hdmi_mode	87
BALENA_HOST_CONFIG_hdmi_cvt	320 240 60 1 0 0 0

In order to demonstrate some visible changes after an update, you can follow these steps:

• In https://github.com/balena-io-projects/multicontainer-demo-rpi3/blob/master/data/index.js
  • Uncomment // data.color = '#FF0000' . This will change the graph from the default blue to a more visible red color.
  • Comment out getRandomTemp(socket); and uncomment // getCpuTemp(socket);. After pushing this change, the graph should be less random, with values around the current CPU temperature. If you provision a local device, you can show off a cool effect by touching the CPU with your finger; the temperature will instantly drop and that will be visible in the graph.