Software for the ESP8266 that sends P1 smart meter data to to MQTT on a configurable topic with json. Easy to consume with Pimatic, Telegraf or other software that supports MQTT. I use a nodemcu for this sketch.
You need to connect the smart meter with a RJ12 connector. This is the pinout to use
Connect GND->GND on ESP, RTS->3.3V on ESP and RxD->any digital pin on ESP with a 10k ohm pull up resistor placed between the RTS/3.3v connection and the data connection. In this sketch I use D5 for the serial communication with the smartmeter.