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Install notes

Urbanova Air Quality Network Sensor Prototype

O/S Setup

Starting with a clean Raspbian Jessie Lite (Sep16) install...

  1. With raspi-config:
    1. Change the password
    2. Set approp locale/kb/tz
    3. Set the hostname Will be set later using Pi's serial number
    4. Enable SPI
    5. Enable I2C
    6. Disable shell on serial port
    7. Enable SSH server (no longer on by default)
    8. Disable wait for network at boot
    9. Advanced > Update
  2. Reboot
  3. sudo apt-get dist-upgrade
  4. install basic utilities: git tmux htop build-essential python-dev python-pip
    • update pip using sudo pip install --upgrade pip
  5. Setup watchdog service
    1. install watchdog
    2. edit /boot/config.txt to contain dtoverlay=watchdog=on ref
    3. fixup the systemd service file thanks to: edit /lib/systemd/system/watchdog.service to contain: 
      [Install]
WantedBy=multi-user.target
    4. edit /etc/watchdog.conf to contain ref 
      watchdog-device = /dev/watchdog
watchdog-timeout = 10
interval = 2
max-load-1 = 24
    5. enable service and start it using sytemctl
    6. finally, test it with a fork bomb: :(){ :|:& };: the Pi should return a PID number, then hang, then reboot
  6. Enable persistent system logs: sudo mkdir -p /var/log/journal ref
  7. enable NPT stats: edit /etc/ntp.conf to uncomment line starting with statsdir ...
  8. Power down and install hardware. If you are working on a different Pi, put the SD card into the correct unit now. All hardware should be assembled as described in the Assembly notes. Once finished, supply power and proceed.

Sensor Software

All hardware must be assembled and attached before proceeding.

  1. Enable real-time clock ref
    1. install: python-smbus i2c-tools
    2. edit /boot/config.txt to contain dtoverlay=i2c-rtc,ds3231
    3. reboot
    4. run i2cdetect 1 and verify 0x68=UU
    5. sudo apt-get -y remove fake-hwclock
    6. sudo update-rc.d -f fake-hwclock remove
    7. edit /lib/udev/hwclock-set to comment out 
      #if [ -e /run/systemd/system ] ; then
#    exit 0
#fi
    8. set clock (check for valid datetime first with date): sudo hwclock -w (read back with sudo hwclock -D -r)
  2. Setup for K30 CO2 sensor
    1. install python-serial
    2. enable the UART: edit /boot/config.txt to contain enable_uart=1
  3. Setup for BMP280 T/P sensor
    1. git clone https://github.com/bastienwirtz/Adafruit_Python_BMP
    2. cd Adafruit_Python_BMP && sudo python setup.py install
  4. Setup for HTU21DF RH/T sensor
    1. git clone https://github.com/raspberrypi/weather-station
    2. use relative imports to obtain the module ref: 
      import sys
sys.path.append('../weather-station/')
import HTU21D
  5. Setup for OPC-N2 sensor
    1. sudo pip install spidev py-opc

Communication Setup

Follow these steps to enable network communications with the Pi Zero over its USB on-the-go (OTG) port.

On the Pi Zero

  1. Enable Ethernet Gadget mode
    1. edit /boot/config.txt to contain dtoverlay=dwc2
    2. edit /boot/cmdline.txt to contain modules-load=dwc2,g_ether directly after rootwait
    3. Reboot
  2. Set static IP on device -- add to /etc/network/interfaces This step superceded by install.sh. 
    allow-hotplug usb0
iface usb0 inet static
    address 10.20.0.2
    netmask 255.255.255.0
    network 10.20.0.0
    broadcast 10.20.0.255
    gateway 10.20.0.1 # upstream computer

On other computers

After enabling Ethernet gadget mode, the Pi Zero will appear to be a usb network adapter to other computers (hosts). It will have a static IP so other hosts can easily connect using standard TCP/IP protocols like SSH and HTTP. The only configuration necessary is to ensure your host is on the same subnet:

Assuming the Pi Zero uses static IP 10.20.0.2/24 per above, the host could select

  • IP address: 10.20.0.1
  • IP subnet: 255.255.255.0

Internet pass-through

To share internet from another Linux computer (host), use dnsmasq per this SE answer.

  1. On the host computer, identify
    • the interface with Internet access (assumed to be eth0 in this example)
    • the interface created by the Pi Zero (usb0 in this example)
  2. On the host computer, assign a static IP to the Pi Zero interface: 
    sudo nano /etc/network/interfaces

    allow-hotplug usb0
iface usb0 inet static
    address 10.11.12.1
    netmask 255.255.255.0
    network 10.11.12.0
    broadcast 10.11.12.255
  3. Install dnsmasq and enable it for the Pi Zero interface: 
    sudo nano /etc/dnsmasq.conf

    interface=usb0
listen-address=10.11.12.1
bind-interfaces
server=8.8.8.8 # or whatever
domain-needed
bogus-priv
dhcp-range=10.11.12.2,10.11.12.100,1h
    Then modify the dnsmasq service file so it continues running even if the network interface is not present: 
    sudo nano /lib/systemd/system/dnsmasq.service

    [Service]
...
Restart=always
RestartSec=30
```
  4. Enable packet forwarding
    • edit /etc/sysctl.conf to enable net.ipv4.ip_forward=1
    • to set immediately: sudo sh -c "echo 1 > /proc/sys/net/ipv4/ip_forward"
  5. Create iptables rules (NB results not saved after reboot; see ref for more details) 
    sudo iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
sudo iptables -A FORWARD -i usb0 -o eth0 -m state --state RELATED,ESTABLISHED -j ACCEPT
sudo iptables -A FORWARD -i eth0 -o usb0 -j ACCEPT

Nginx Reverse Proxy

For details on the testing configuration which included an Nginx reverse proxy, see this Gist.

RPi-Monitor Integration

For small projects, RPi-Monitor is a good quick-and-dirty solution that achieves:

  • local system monitoring (cpu, disk space, uptime, etc)
  • round-robin database storage (rrdtool)
  • web interface (no SSH req'd for monitoring)
  • plotting (with time zoom)

The documentation is not spectacular, but it's easy to get started (copied from the debian packaage install docs):

sudo apt-key adv --recv-keys --keyserver keyserver.ubuntu.com 2C0D3C0F
sudo wget http://goo.gl/vewCLL -O /etc/apt/sources.list.d/rpimonitor.list
sudo apt-get update
sudo apt-get install rpimonitor

Open a web browser and navigate to http://10.11.12.13:8888. There should be a warning about "Update needed...". Pull updates and enable automatic updates to keep current:

sudo /etc/init.d/rpimonitor update
sudo /etc/init.d/rpimonitor install_auto_package_status_update

Now copy the relevant modified template files into the appropriate folder.

Hasn't been integrated into the install script yet.

sudo cp etc/rpimonitor/* /etc/rpimonitor/

Software TODO

  • replace manual log file creation with logging or logbook
    • even better, store data into database instead of flat files
  • use non-blocking timing mechanism
    • replace sleep with recursively launched function
    • a threaded helper for each sensor?
  • properness
    • turn off OPC-N2 at script exit

For demonstration purposes

Notes from setting up update meeting demo unit.

autostart options that don't work well:

  • cron @reboot (maybe worth retrying)
  • .bashrc (starts for every shell session)
  • /etc/rc.local (no errors, no output)
  • systemd service (can uncapture stdout but requires restart after boot to see output; oddly, can see output in boot messages but not once login presented?)