RasPi based S0 powermeter sampling + remote graphing tool
This part needs the "wiringPi" library and should be otherwise independent from any further tools. Contact me if you find any further dependencies. The main idea is to keep this as simple as possible.
git clone git://git.drogon.net/wiringPi
cd wiringPi/
./build
Once the library is installed, you can (hopefully) build the s0 binary by just executing "make" in the "s0" folder.
The configuration is very simple, it consists of one file: s0.ini (example included)
Each line in this file is either a GPIO configuration or a specific file to save the counters.
#0,0,1000
Two settings are needed here:
LAST is the file where the most recent counters are saved. This one must be on a RAM disk, otherwise your SD card will be written to death pretty quickly.
SAVE is the file which keeps the values over reboots, this needs to be on a reboot-safe filesystem.
The "LAST" file (/var/run/s0.last) is currently hardcoded in the s0 binary, but you can change it by changing the line #define FILENAME "/var/run/s0.last" to what ever you desire and re-compiling the binary.
LAST=/var/run/s0.last
SAVE=/var/cache/s0.last
A start/stop script is already shipped with the project: s0.sh
It takes care about starting/killing the binary as well as syncing the data to and from the reboot-safe location.
Even if the counters should be automatically saved and restored by the script, it makes sense though, to use a cron job to periodically sync the counters in RAM to the disk, so that the values are not completely lost in case the Pi crashes. To save your memory card's life-span it's recommended to do this either daily or if needed hourly. (8760 writes/year if done hourly - an SD card should survive this for several years, if it's a reliable one. You will probably find lots of articles & tests about this topic online.)
(TODO)