Build requirements:

• Arduino IDE 1.8.13
• Arduino ESP8266 package 3.0.2
• Arduino library ESPAsyncTCP https://github.com/habazut/ESPAsyncTCP/tree/fix
• AsyncMqttClient library https://github.com/marvinroger/async-mqtt-client.git

Needs a credentials.h with

 #define WIFI_SSID "FOO"
 #define WIFI_PASSWORD "BAR"

Hardware (schematics etc) found on: https://github.com/psvanstrom/esphome-p1reader