[[File:FlashlightPIN.png|alt=https://www.youtube.com/watch?v=zqpaXnFCUYQ|thumb|entering PIN with a flashlight]]
[[File:SM reader writer.png|alt=https://amzn.eu/d/c23GH7Z|thumb|Tasmota based reader writer]]
Most smart meters in Germany are equipped with an bidirectional ifrared-port (actually two ports: one for TX and one for RX) for sending and receiving data. This port will send additional metering information if activated. This includes momentary power import/export to and from the grid and voltage in different phases (L1, L2, L3). Activation is protected by a 4-digit PIN, which is (for data protection reasons) only available from the company owning the meter, or if unconfigured "0000" as a factory default. To activate the sending of additional metering data, the pin has to be entered by using a simple flashlight. Here's a [https://www.youtube.com/watch?v=zqpaXnFCUYQ video] showing, how this is done. PIN protetion can be permanaently deactivated. After successfull activation, the meter can be configured by sending serial communication commands via the ir port either by SML or OBIS protocol (ASCII or binary (SML) depending on the meter). After configuration the meter will transmit the information requested via the ir-port. Users communicate with these meters via diy-style serial opto-couples via cable link or WiFi. Freely available [https://www.tasmota.info/ Tasmota] (github) software based soultions do make use of inexpensive microcontrollers (ESP8266 or ESP32) for that purpose. There is a description of the smart meter interface API, running an OBIS-Protocol [https://tasmota.github.io/docs/Smart-Meter-Interface/ here].