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This topic details a mini project using the EON Energy Monitor:


EON have being given them away “free” when you sign up to getting energy from them. It is infact a re-branded Current Cost Energy Monitor.

I noticed that on the bottom was an RJ45 connector, after a bit of Googling, I found this and this.

So using Chris Hand's infomation, the interface on the RJ45 is:

  • orange/white
  • orange
  • green/white (pin 7, data in to CurrentCost)
  • blue (pin 4, ground)
  • blue/white
  • green
  • brown/white
  • brown (pin 8, data out from CurrentCost)

The level is 3.3v TTL so cannot be connected directly to an RS232 port, however I don't have one of them free anyway, so I used a USB to TTL 3.3v serial converter (also used by Chris Hand) from RS (part number 429-307). Current Cost do sell the cable for a good price, but what is the fun in that!!!

Using an old Ethernet cable for an RJ45, connecting the USB to serial convert to the RJ45 connector was easy:


Just connect the pin 4 (blue) of the RJ45 to pin 1 (black) on the TTL-232R-3V3 and connect pin 8 (brown) of the RJ45 to pin 5 (yellow) on the TTL-232R-3V3. If I get time I will make a better cable, but for now this works.


When the hardware connected, I used Minicom to check that it was working. There are two version of currrentCost available, one that runs at 2400 baud, and one that runs at 9600. Mine was a 9600.

The device spits out XML data every 6 seconds. You do not need to request data.

I wrote a simple c program to read the XML stream and convert into a CSV file that gnuplot can understand.

The code can be found here

This application runs on my Linux server and reads and converts the XML stream into the CSV file, I also have a cgi script to convert the CSV file into a picture.

This is an example plot:


energymonitor.txt · Last modified: 2016/04/08 09:25 (external edit)