DSMR Logger V4 (Smart Meter Reader)Placed on
The telegram is sent by the Smart Meter via pin 5 of the RJ12 connector with an inverted 5volt TTL logic. For the ESP8266, this signal must be inverted (back) as well as made suitable for 3v3 logic of the ESP8266.
At rest, R6 will be the Base of Q1 “high” pulling, leaving Q1 “Closed” becomes and the Collector, and with it Rx_SM “low" will be. If Tx_SM “low” is will the Base of Q1 also “low” will be and will be Q1 “Open" go stand. The Collector and with it Rx_SM will be pulled to 3v3 by R8. Rx_SM is then “high”. Does Tx_SM come with a “high” signal in, then the Base of Q1 will also “high" become. This causes Q1 to conduct and the Collector together with Rx_SM “low" become.