Get started with Raspberry Pi 3 and Python
In this guide we will build a simple Python web server project on a Raspberry Pi 3. At its most basic, the process for deploying code to a Raspberry Pi 3 consists of two major steps:
- Setting up your Raspberry Pi 3 with balenaOS, the host OS that manages communication with balena and runs the core device operations.
- Pushing your Python project to the balena image builder, which pulls in all necessary dependencies and creates the container image for your application.
Once these steps are finished, your Raspberry Pi 3 will download the container image, kick off your application, and begin sending logs to your balena dashboard!
What you will need
- A Raspberry Pi 3 Model B or B+. See our supported devices list for other boards.
- A 4GB or larger microSD card. The speed class of the card also matters - class 10 card or above is the way to go.
- A micro USB cable.
- [Optional] An ethernet cable.
- [Optional] A 2A micro USB power supply.
- A balena account.
If you find yourself stuck or confused, help is just a click away:
- The balenaCloud section of the forums is where our engineers address any issues you may be having with balena.
- You can read more about our approach to support here.
If you don't already have a balena account, make sure to sign up.
Adding an SSH Key
Balena uses git to push code from your computer to a dedicated repository. As part of the account creation process, you will be asked to add a public SSH key. The SSH key secures your connection to our server, letting us know you have the authority to make changes to the repository.
Note: You can click Skip to move past this step for now, but you will not be able to push code to your Raspberry Pi 3 until you have added a public key to your account. This can be done at any time from the Preferences page on the dashboard.
If you have a public SSH key, simply paste it into the box provided and click Save Key:
You can also import your key from GitHub. If you choose this option, you will be asked to enter your GitHub username:
Don't have an SSH key?
If you are unfamiliar with SSH keys, we recommend you take a look at GitHub's excellent documentation. This will walk you through everything you need to create a key pair. Window's user? Be sure to check out these instructions.
Create an application
An application is a group of devices that share the same architecture and run the same code. When you provision a device, it is added to a specific application, but can be migrated to another application at any time.
To create an application, select the Raspberry Pi 3 device type, select an application type, enter a name, and click Create new application:
Note: To create an application with multiple containers, you'll want to use the starter or microservices application type. The starter applications are full-featured and free for all users, with a limit of up to ten total devices across all starter applications.
This will take you to the dashboard for your newly created application, where you can manage your whole fleet of Raspberry Pi 3s.
Add your first device
To connect with balena, your Raspberry Pi 3 will need a balenaOS image that is configured for your device type, application, and network. Start by clicking Add device in your application dashboard:
For most applications, you will have the option to select a device type. By default, the device type you chose when you first created the application will be selected. Applications can, however, support any devices that share the same architecture, so you can choose another device type if needed.
After selecting a device type, you will see a list of available balenaOS versions. In general, the most recent version is recommended. You can also select whether you would prefer a Development or Production edition with the respective toggle:
Note: When you're first getting started, a Development image will be most useful, as it permits a number of testing and troubleshooting features. For production use, be sure to switch to a Production image. More details on the differences between Development and Production images can be found here.
A toggle is also used to select whether your network connection will be through Ethernet Only or with the option for WiFi + Ethernet. Selecting Wifi + Ethernet allows you to enter a WiFi SSID and WiFi Passphrase:
Clicking Advanced presents the option to select the rate at which your device checks for updates and the option to download just a configuration file (
config.json) rather than an entire image:
Once you have finished your image configuration, click the Download balenaOS button. When the download completes, you should have a zipped image file with a name like
FirstApp is the name you gave your application on the dashboard.
The next step is to flash the downloaded image onto your SD card using Etcher, a simple, cross platform SD card writer and validator. Once you have Etcher installed, start it up. To give Etcher access to your SD card, your system may prompt you to grant administrative privileges.
To create a bootable balenaOS SD card follow these steps:
- Click Select image and find your application's balenaOS image file.
- If you haven't already done so, insert your SD card into your computer. Etcher will automatically detect it. If you have more than one SD card inserted, you will need to select the appropriate one.
- Click the Flash! button.
Etcher will now prepare a bootable SD card and validate that it was flashed correctly. This can take roughly 3 or more minutes depending on the quality of your SD card. You'll get a little ping when it's done, and Etcher will safely eject the SD card for you.
Note: You can burn several SD cards with the same image file and all the devices will boot and provision into your application's fleet. You can also disable the auto-ejecting or validation steps from the Etcher settings panel.
Provision your device
Insert the SD card into your Raspberry Pi 3 and connect the ethernet cable if necessary. Now power up the Raspberry Pi 3 by inserting the micro USB cable.
It will take a minute or two for the Raspberry Pi 3 to appear on your balena dashboard. While you wait, the balenaOS is expanding the partitions on your SD card to use all available space, installing a custom Linux environment, and establishing a secure connection with the balena servers.
You should now be ready to deploy some code!
Note: Class 4 SD cards can take up to 3 times longer so it's well worth investing in the fastest card you can find.
Help! My device won't show up.
If your device still hasn't shown up on your dashboard after a few minutes, something is definitely wrong. First check that you entered the WiFi credentials correctly and ensure that your network meets these basic requirements. It may also be worth checking the LED error notifications
If you still can't get your device online, come on over and talk to us on our support channel.
Note: If you have an HDMI screen attached, you should see
"Booted - Check your balena dashboard." on the screen when the device boots. If instead you see rainbow colours or a black screen with 4 raspberries on it, it could mean that the SD card was not burned correctly or is corrupted.
Now that we have a device or two connected to a balena application, let's deploy some code and actually start building something.
To clone the project, run the following command in a terminal or your preferred git client:
$ git clone https://github.com/balena-io-projects/simple-server-python.git
Once the repo is cloned, change directory into the newly created
simple-server-python directory and add the balena git remote endpoint by running the command
git remote add shown in
the top-right corner of your application page:
$ cd simple-server-python $ git remote add balena <USERNAME>@git.balena-cloud.com:<USERNAME>/<APPNAME>.git
Note: On other git clients there may be an alternative way to add a remote repository.
So now we have set up a reference in our local git repository (the one on our development computer) to the balena application remote repository. So when we push new changes to this remote repository it will get compiled and built on our servers and deployed to every device in the application fleet.
Warning: The balena git repository is not intended as a code hosting solution, and we cannot guarantee the persistence of data in balena git remotes.
Now to deploy this code to all device(s) in the application just run the command:
$ git push balena master
If you want to completely replace the source code of the application with a new source tree, you may need to force the push by running
git push balena master --force, due to how git works.
Note: On your very first push, git may ask you if you would like to add this host to your list of allowed hosts. If the ECDSA key fingerprint matches
SHA256:NfwmqnKId5cx1RWpebbEuuM87bCJbdyhzRnqFES9Nnw, you are pushing to the right place. Type 'yes' to continue.
You'll know your code has been successfully compiled and built when our friendly unicorn mascot appears in your terminal:
This means your code is safely built and stored on our image registry. It should only take about 2 minutes to build your code and subsequent builds will be quicker because of build caching.
Your application will now be downloaded and executed by all the devices you have connected in your application fleet. You may have to wait about 6 minutes for the first push... So time for more tea, but don't worry, all subsequent pushes are much, much faster due to Docker layer sharing. You can see the progress of the device code updates on the device dashboard:
You should now have a Python web server running on your device and see some logs on your dashboard. If you go to the
Actions page for your device, you can enable a public URL, this URL is accessible from anywhere in the world.
If you follow the URL, you will be served a page saying "Hello, World!". Alternatively you can point your browser to your devices IP address.
- Learn more about the Dockerfile that is used to build your application.
- Build an application that uses multiple containers.
- Get to know the web terminal, which can be used to SSH into your application containers and the host OS.
- Try out local mode, the most efficient way to rapidly develop and test your balena application.
These example projects will give you an idea of more things that can be done with balena:
Basic GPIO Control in Python
This sample project will get you started blinking LEDs on the Raspberry Pi 3 using Python. For this project you will need some additional hardware, namely a few LEDs, a breadboard and a 220 ohm resistor.
I2C Accelerometer Example
This is a simple Python project that uses i2c to read acceleration data from the ADXL345 sensor. It is made to be generic and act as base for any i2c sensor integration.
This Python project allows you to share your ethernet connection to wifi. It creates a WiFi hotspot by talking to connman over dbus.
This is a simple project so show to read analog sensor values into the raspberry pi using Python. It uses the ADS1x15 family of I2C analog-to-digital converters to read in analog signals between 0 and 3.3V.
RPI camera module example in Python
Enjoy Balenafying All the Things!