thorberry

Lightning watch system using

• RPi
• Ruby on Rails
• Thorguard
• pi_piper gem
• piface gem

Setting Up thorberry on RPi

The setup script is included in setup/. An Internet connection is needed to run the script.

Here are the things that the script does:

• sudo apt-get update && sudo apt-get upgrade
• enable spi
• add the user pi to groups gpio and spi
• install git, nodejs, nginx, and ruby (>= 2.x) (Ruby With RVM)
• install bundle and rails gems
• git clone thorberry
• run bundle install and bundle exec rake db:migrate db:seed inside the cloned directory
• edit pi_piper
• set up Nginx
• set up systemd

Setting Up Nginx

An example configuration file looks like this:

upstream thorberry {
    server localhost:3000;
}

server {
    listen 80 default_server;
    server_name _;

    keepalive_timeout 5;

    root /home/pi/thorberry/public;
    access_log /home/pi/thorberry/log/nginx.access.log;
    error_log /home/pi/thorberry/log/nginx.error.log info;

    location / {
           proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $http_host;
        
        if (-f $request_filename) {
            break;
        }
        
        proxy_pass http://thorberry;
       }
}

You will have to disable the default server on 80.

piface Gem Output Pin Numbering

piface's README says that the relays can be accessed with pin 1 and 2. However, the correct pin numbers are 0 and 1 for the relays.

Setting Up Systemd

Here is an example systemd file.

# /etc/systemd/system/thorberry.service

[Unit]
Description=thorberry
Requires=network.target

[Service]
Type=simple
User=pi
WorkingDirectory=/home/pi/thorberry
ExecStart=/bin/bash -lc 'bundle exec rails server'
Restart=always

[Install]
WantedBy=multi-user.target

After setting up Nginx, run systemctl enable nginx thorberry.

Default Logins

Administrator: thor / sonofodin
Guest: loki / notsonofodin

This information can be changed in db/seeds.rb.

pi_piper Issues

pi_piper "/dev/mem: Permission denied" fix

The solution is to replace libbcm2835.so in /path/to/gems/pi_piper-2.0.0/lib/pi_piper/. The replacement file is provided in setup/.

pi_piper "Permission Denied @ rb_sysopen" workaround

The problem turned out to be some kind of a race condition between the script and the file creation. It seemed to have only happened to me, but I was getting the error every single time. Right after the GPIO pins are exported, the files in the newly created directory are not accessible by the gpio group.

For now, I applied a cheap workaround.

# In /path/to/gems/pi_piper-2.0.0/lib/pi_piper/bcm2835.rb

def self.export(pin)
  File.write('/sys/class/gpio/export', pin)
  sleep 0.1 # to prevent race condition that gives EACCESS
  @pins << pin unless @pins.include?(pin)
end

pi_piper "/sys/class/gpio/export EBUSY" workaround

The problem arises because I cannot think of a good way to keep the GPIO pin instances alive. When the PiPiper::Pin.new is called on a pin that is already exported, the EBUSY error occurs.

My workaround is to tweak the pi_piper's export method. The final export method is shown below.

# In /path/to/gems/pi_piper-2.0.0/lib/pi_piper/bcm2835.rb

def self.export(pin)
  return if @pins.include?(pin)
  
  File.write('/sys/class/gpio/export', pin)
  sleep 0.1 # to prevent race condition that gives EACCESS
  @pins << pin
end

Keep in mind that this is a workaround, not a fix.