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Alternative way of using Chumby monitoring energy usage.
Before getting a Chumby/Flukso owner i was monitoring my power with CurrentCost. http://umweltsuende.wordpress.com/2010/04/03/currentcost/ CurrentCost Envi is a low cost energy monitor from UK. You can order them easily via ebay or amazon.
CurrentCost Envi seems a little bit more inaccurate than Flukso, but you can read the 3 power channels individually. I like it an i don´t want to trash it because i have a flukso now. My setup is running extremely well and stable for months :)
Since i`m spending some thoughts on how to monitor power without a home-server, internet connection or wifi, i wanted to give chumby a try to replace the role of my home server for monitoring.
What can i tell?
Success ! It`s not too hard to do that.
The hardest part is to get missing binaries like stty and rrdtool for ARM9. Since i don`t have yet a cross-compile environment for ARM9 i searched some time to find appropriate coreutils and rrdtool packages providing binaries which run on chumby. I had success at http://downloads.buffalo.nas-central.org/
How to proceed ?
Just plugged in my currentcost usb cable into the chumby and….. surprise - it`s immediately being recognised without any further action ! Chumby comes with pl2303 kernel driver for the usb2serial bridge of the currentcost cable.
After that, set appropriate serial line speed with stty -F /dev/ttyUSB0 speed 57600 (stty comes with coreutils package) and then tested with “cat /dev/ttyUSB0” and immediately saw the currentcost XML output….
Great!
Now use your favourite perl script for reading data from /dev/ttyUSB0 and put that into rrdtool. There are many ways to do that and that`s already documented several times on the web. If you want some help please leave me a note (devzero AT web.de)
But how to show the rrdtool graphs on the chumby ? I can´t program Adobe Flash… :(
Here comes the trick: Chumby comes with busybox httpd - you just start another instance on another port with another homedir:
httpd -p 8080 -h /tmp/mydir
Then go to mychumby and add one of those “show me a picture from an url” widgets to your channel point the url to http://localhost:8080/path/to/image
You need to scale the rrdtool graphs appropriately so they look nicely on the chumby (320x240px) - a little bit trial and error to find the correct size as the older rrdtool from nas-central.org has no support for ”–full-size-mode” which would make life easier…..
so, that`s just some quick info because gonium asked for it. maybe i`m adding stuff/details later on…. (I`m awful in writing docs and i have to admit that i hate it :D )
Roland
