• Pi Version: Raspberry Pi 3 B+
• PiOS Version: Raspberry Pi OS (32-bit) 2020-08-20
• Date: 2020/10/23

A Note: These are my notes to help me streamline the process of readying a Raspi for development or project work. Your use and therefore your process may vary. My engagement with the Pi is episodic and these notes may fall out of date as new technology and new tools may emerge.

I frequently use Raspberry Pis to serve as a behind-the-scenes controller for projects. In the last several years, the Pi has controller for:

• A retro gaming system
• A "chicken robot" to open and close the doors of our chicken coop, and serve IR camera images so we could confirm the door was closed and everyone accounted for
• An audio and visual piece at Burning Man
• Controller for a musical instrument and LED controller for another piece at Burning Man
• A smart video sequencer/player for art exhibitions
• A primary controller and video/audio player with various arduino secondaries to control peripherals in an art installation
• A "time machine" radio that allowed you to tune in to various radio stations that represented different eras and styles

In all these cases, the Pi was the obvious choice because of its incredible adaptibility and modularity, including:

• standard Unix OS/Debian
• ability to run python and its many useful modules
• Chromium browser with leading edge JavaScript support
• Wifi and Bluetooth
• GPIO access to control hardware
• selection of various inexpensive hats/peripheral boards
• Capable processor
• HDMI, ethernet, and USB connectors

In the past, I'd imaged my Pi SD card from the command line because there was not a mature card imager (let alone one specifically for Raspberry OS) for MacOS.

1. Go to https://www.raspberrypi.org/documentation/installation/installing-images/
2. Go to section "Using Raspberry Pi Imager"
3. Download the latest version of Raspberry Pi Imager
4. Install and run
5. Install the latest version of Raspberry Pi OS (formerly Raspbian) to your SD card

Voila! Simple as Pi.

We'll be doing the basic configuration through the GUI. So install the SD card, plug in a monitor, keyboard, and mouse, and power it up.

1. Go through the startup menus, choosing your language, password, wireless network, etc
2. Allow the Pi to update to the latest software and packages
3. Go to Pi Menu > Preference > Raspberry Pi Configuration
4. Under the Systems tab, rename your system
5. Under the Interface tab, Enable SSH and any other interfaces you need to enable
6. Reboot as necessary

We no longer have to make sure that the OS has the full use of the SD Card, as this is done when the system first boots and the options has been removed from the raspi-config menus.

But we can still reclaim some space:

$ sudo apt-get purge libreoffice*
$ sudo apt-get clean
$ sudo apt-get autoremove

On Raspberry Pi OS Stretch, remote power management is on by default. Why? It couases WiFi to occassionally drop. Let's turn it off.

Use this command to read the current power saving mode of your Pi:

sudo iw wlan0 get power_save

And this one to turn power_save off:

sudo iw wlan0 set power_save off

To make this permanent add the following line to /etc/rc.local:

/sbin/iw dev wlan0 set power_save off

We'll use git and github to manage our development. This allows us to code on our favorite development machine/IDE/editor, push changes, and pull them down to the pi.

Create your github.com repo for whatever development you plan to do.

1. + (in upper right corner near profile) > New repository
2. Name it, add a README, .gitignore, etc
3. Create Repository

On the pi's command line, create an ssh key so we can clone from github.

1. Open up the pi terminal and run:

   cd ~/.ssh && ssh-keygen

2. Show your public key with

   cat id_rsa.pub

3. Select and copy

4. On the github.com website, go to Profile (upper right) > Settings > SSH and GPG keys > New SSH Key, paste in your SSH public key

Finally, back at the command line, setup your .gitconfig.

1. git config --global user.name "Wes Modes"

2. git config --global user.email "[email protected]" (don't forget to restart your command line to make sure the config is reloaded)

Now let's clone our new repo.

1. From your repo on github.com, hit the Code Button and copy the SSH Clone link

2. Back on the pi's command line

   mkdir ~/dev`
   cd ~/dev
   git clone [email protected]:wmodes/chickenrobot.git (pasting in your link, of course)
   cd chickenrobot
   

3. Do the same thing on your develepment machine to clone the repo

Later after we do some coding on our fave development playform and push those changes to our upstream repo, we can pull them down on the pi with

`git pull`

For convience, this is also a good time to make it easier to login to your pi. From your dev machine:

`% ssh-copy-id -i ~/.ssh/id_rsa [email protected]`

This assumes you already have an ssh key generated on your machine, which is likely.

By default the pi has Python 2 set as the default. This is irritating. Let's fix it.

Let's find what versions we have:

$ python --version
Python 2.7.16
$ python3 --version
Python 3.7.3

To change python version system-wide we can use update-alternatives command. Logged in as a root user (use sudo su), first list all available python alternatives:

# update-alternatives --list python
update-alternatives: error: no alternatives for python

The above message means that no python alternatives have been recognized by update-alternatives command. For this reason we need to update our alternatives table and include both python2.7 and python3.7:

# update-alternatives --install /usr/bin/python python /usr/bin/python2.7 1
update-alternatives: using /usr/bin/python2.7 to provide /usr/bin/python (python) in auto mode
# update-alternatives --install /usr/bin/python python /usr/bin/python3.7 2
update-alternatives: using /usr/bin/python3.7 to provide /usr/bin/python (python) in auto mode

The --install option takes multiple arguments to create a symbolic link. The last argument specified priority, with a higher number being higher priority. Let's check the alternatives:

# update-alternatives --list python
/usr/bin/python2.7
/usr/bin/python3.7

Nice. And finally, let's check the default versions of python and pip:

# python --version
Python 3.7.3
# pip --version
pip 18.1 from /usr/lib/python3/dist-packages/pip (python 3.7)

Woot.