Reads optical interface (IEC62056-21) from a LOGAREX LK13B using a Arduino Nano V3 clone and a BPW42 transistor
The wiring diagram is given in iec62056-21_Schaltplan.png.
A basic parser&storage Python script is given in: https://github.com/mh-g/powermeter