Monday, 27 March 2017

HOME AUTOMATION: OpenHAB2 Serial Binding on Raspberry Pi

I have always wanted to enable my home automation setup with per-room presence detection. With this in mind I purchased and installed an ELK/NESS home alarm with automation capability.

I haven't been able to find any decent OpenHAB binding for the alarm, and after recently giving up on getting my M1XEP serial to network box for my alarm working I've decided to try my hand at rolling my own serial solution. Here I'll discuss how I got the serial configuration up and running.


Install the binding from the configuration GUI

I'm using a USB to Serial adapter, but other serial devices should also show up as serial devices if they have been recognised by the kernel. You can check this with the command:

Or to view messages relating to the serial port configuration use the command:
 dmesg | grep tty
This should tell you what port was assigned to your USB to Serial adapter, in my case ttyUSB0

Check which users have access to the serial port with the command:
 ll /dev/ttyUSB0  

Output should look something like:
 crw-rw---- 1 root dialout 188, 0 Mar 27 10:03 /dev/ttyUSB0  

You may need to add the default user to the dialout group:
 sudo adduser openhabian dialout  

It's a good time to check the serial connection to make sure it's working as expected. You can use the GNU screen command to view the serial port from the command line:
 screen /dev/ttyUSB0 115200  

The screen command won't exit with the typical commands like CTRL-X or CRTL-Z, to exit the screen command enter 'CTRL-a' then press '\', then hit 'Y' to exit the screen.

Now that we have the binding installed and confirmed the serial port is working as expected we can continue with the OpenHAB setup

OpenHAB2 Configuration 

I created and 'alarm.items' file to store alarm related configuration info:
 Switch AlarmUpdate "Alarm Update" { serial="/dev/ttyUSB0@115200" }  
 String AlarmMessage "Alarm Message" { serial="/dev/ttyUSB0@115200" }  

and a 'alarm.rules' file with the following:
 ule "Interpret Alarm Command"  
     Item AlarmMessage received update  
     logDebug("alarm", "Alarm message updated")  

Check everything is working with the command:
 tail -f /var/log/openhab2/openhab.log -f /var/log/openhab2/events.log  

And you should see log messages like the following:
 2017-03-27 12:08:27.946 [ItemStateChangedEvent   ] - AlarmMessage changed from 0AZC007200C9  
  to 16XK2708212270117011006C  

Now that the serial binding is working we can move on to interpreting the data!

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