I found a great blockchain.py project on Github this week. The first challenge is the requirement for the very latest version of Python 3.6 or higher.

Learn Blockchains by Building One

I found a the instruction and started work on a newly installed headless Raspberry Pi server.

Installing Python 3.6.2 on raspberry pi (raspbian)

Start by upgrading the build environemnt.

sudo apt-get update 
sudo apt-get install build-essential tk-dev libncurses5-dev  
sudo apt-get libncursesw5-dev libreadline6-dev libdb5.3-dev  
sudo apt-get libgdbm-dev libsqlite3-dev libssl-dev libreadline6-dev 
sudo apt-get libdb5.3-dev libgdbm-dev libsqlite3-dev libssl-dev 
sudo apt-get libbz2-dev libexpat1-dev liblzma-dev zlib1g-dev

Next, download the latest version and make python3.6.3

wget https://www.python.org/ftp/python/3.6.3/Python-3.6.3.tar.xz 
tar xf Python-3.6.3.tar.xz 
cd Python-3.6.3
./configure --enable-optimizations 
make 
sudo make altinstall

Now to test

Introduction

I didn’t like Python when I was first introduced to it a couple of years ago. Since that time I’ve learned that it is a great quick-n-dirty language that can be used to build an app or what we used to call a “hack”. The extent of its built-in features and the enormous amount of open source code makes it a natural do-it-yourself language.

Install Tool Chain or Installation Scripts

The first step is to install several tools to facilitate installation of Python modules.

sudo apt-get install -y python-pip git
sudo apt-get install -y build-essential python-dev python-smbus
sudo apt-get install i2c-tools

I like to use Flask so install the following for a basic environment.

sudo pip install flask 
sudo pip install requests 
sudo pip install flask-httpauth

My do-it-yourself home automation system uses MQTT for messaging. My Python apps subscribe and publish using the Paho implementation.

sudo pip install paho-mqtt

I like to use Adafruit’s I2C backpack for LED and OLED devices. Their libraries usually require the Python imaging module.

sudo apt-get -y install python-imaging python-pil

Add Adafruit libraries for the most common devices. I like to use the GPIO, LED backpack and OLED displays for almost every project.  Upgrade pip to use setup wheel

sudo python -m pip install --upgrade pip setuptools wheel

Start with the GPIO stuff. I like to use a directory called /home/pi/systemd.

mkdir systemd
cd systemed
git clone https://github.com/adafruit/Adafruit_Python_GPIO.git
cd Adafruit_Python_GPIO
sudo python setup.py install

Add OLED python class:

git clone https://github.com/adafruit/Adafruit_Python_SSD1306.git
cd Adafruit_Python_SSD1306
sudo python setup.py install

Add the LED backpack class:

git clone https://github.com/adafruit/Adafruit_Python_LED_Backpack.git 
cd Adafruit_Python_LED_Backpack
sudo python setup.py install

Sync and reboot. The next step depends on your project device.

Each Internet of Things (IOT) device in my Do It Yourself Home Automation System (Diyhas) has three elements.

1. Headless Raspberry Pi server with Wi-FI and Bluetooth (Pi Zero W for example)
2. Build and production Python directory structure with my device or subsystem Python modules and a variety of Open Source modules.
3. Boot configuration using systemctl

The systemctl process is used to manage the IOT application.

Configuring a Basic systemctl Service Configuration File

I’m going to use my basic DiyhasClock.py application as an example. My basic file structure requires to three directories: ../fonts, ../logs and ../systemd. The DiyhasClock service requires a configuration file called DiyhasClock.service. This file has three sections:

• [Unit] — contains options not dependent on the type of the service. It contains directives like description, service behavior and dependencies with other services.
• [Service] — categorizes services by their process and daemonizing behavior
• [Install] — optional and defines the behavior if the service is enabled or disabled

The first step is to create a service configuration file in development directory.

cd /home/pi/systemd
vi DiyhasClock.service

The first section of the configuration file contains a [Unit] with a simple Description and the After directive which states that it requires multi-user run level.

[Unit]
Description=DiyhasClock
After=multi-user.target

The [Service] section has two directives. The Type specifies that the service runs after the boot sequence is complete, i.e., idle. The ExecStart is the full command and path to execute. In my case I use Python, the directory of the Python code and a log file.

[Service]
Type=idle
ExecStart=/usr/bin/python /home/pi/systemd/DiyhasClock.py > /home/pi/logs/DiyhasClock.log 2>&1

The remaining section is used to add DiyhasClock.service to the multi-user run level when the Raspberry Pi server is booted.

[Install]
WantedBy=multi-user.target

The next step is to move the completed DiyhasClock.service to the systemctl directory.

Adding the DiyhasClock Service to the Boot Sequence

The next steps are relatively simple. Move the DiyhasClock.service to the systemctl directory and enabling the service.

sudo cp DiyhasClock.service /lib/systemd/system/DiyhasClock.service
sudo chmod 644 /lib/systemd/system/DiyhasClock.service
sudo systemctl daemon-reload
sudo systemctl enable DiyhasClock.service

Reboot and test the installation. For convenience I always create an aliases file to manage my IOT applications.

cd 
vi .bash_aliases

The file contains the following systemctl specific aliases.

alias stop='sudo systemctl stop DiyhasClock.service'
alias status='sudo systemctl -l status DiyhasClock.service'
alias start='sudo systemctl start DiyhasClock.service'
alias restart='sudo systemctl restart DiyhasClock.service'
alias catlog='cat /home/pi/logs/DiyhasClock.log'
alias taillog='tail -f /home/pi/logs/DiyhasClock.log'

That’s how I manage an IOT production device.

Introduction

Every time I receive a new Raspberry Pi, I go through the same error prone discovery process of creating my personal development environment. I know its going to be Python based with Flask, Paho MQTT, Adafruit modules, my own Python models and a standard pi user file structure. I also setup a “systemd” init configuration and modify the .bash_aliases file with “status”, “restart”, “stop”, etc. to manage the process started by the boot sequence.

Since I don’t have the space to add a USB keyboard and mouse to my already crowded desk, I’ve settled on headless servers. IMHO a headless Raspberry Pi server is also an ideal Internet of Things host. This “how to guide” is for Mac OS users like myself.

Getting Started

Go to the Raspberry Pi download page, select the latest “lite” image. You will need to unpack or unzip the file.  Raspian Lite Image

Use Etcher to copy the img file to your SD card. It is usually /dev/disk2. Use Etcher to burn the img to the SD card

Ok, now the fun begins. A headless server needs SSH enabled. Simply create an empty file call “ssh” on the boot level.

cd /Volumes/boot
touch ssh

If you can’t see /Volumes/boot try reinserting the SD card.  You should see the boot volume on Finder.

I’ve standardized on Wi-Fi for most of my devices, which is a must for the Raspberry Pi Zero W. The next step is to configure your local Wi-Fi access point.

vi wpa_supplicant.conf

Insert the following into the blank file on the boot level. NO SPACES! Don’t forget to use the correct SSID and PASSWORD.

ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1
network={
ssid="SSID"
psk="PASSWORD"
key_mgmt=WPA-PSK
}

Eject the SD card using finder. Insert it into your Raspberry Pi, power it up and cross your fingers!

First Login to Pi Zero

Special instructions for the Raspberry Pi Zero are needed to attach a Wi-Fi dongle to the USB port. First connect your Pi Zero to your network with a RJ45 connector. Boot the Pi Zero and update/upgrade the OS to support USB/Wi-Fi.

sudo rpi-update
sudo apt-get update
sudo apt-get -y upgrade
sudo apt-get -y dist-upgrade

If you get a command not found error on the rpi-update then simply install it with apt-get. Some earlier distributions did not include this command.

sudo apt-get install rpi-update

The latest kernel has changed the /etc/network/interfaces file to use /etc/network/interfaced.d files. What I found that works is to add the following lines to the end of the /etc/network/interfaces file.

cd /etc/network
sudo vi interfaces

Add the following to the end of the file.

allow-hotplug wlan0
iface wlan0 inet manual
    wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

allow-hotplug wlan1
iface wlan1 inet manual
    wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

This may mess up dhcp but I’ve just started working with the Pi Zero USB/Wi-Fi.

First login to Pi Zero W

Login the new server and run raspi-config to set password, hostname and enable I2C.

ssh pi@raspberrypi.local
sudo raspi-config

• Change the password and hostname
• Expand memory
• Enable the camera, SPI and I2C bus
• Set timezone and localization
• Exit and reboot

Update the operating system with latest.

sudo rpi-update
sudo apt-get update
sudo apt-get -y upgrade 
sudo apt-get -y dist-upgrade
sudo sync
sudo reboot

Configure the Apple Bonjour service and Apple networking

sudo apt-get install avahi-daemon
sudo systemctl enable avahi-daemon.service
sudo apt-get -y install netatalk

Edit the .bashrc file to enable ll and other aliases. See systemctl

vi .bashrc
sudo sync
sudo reboot

Reboot and test your installation.