Analog data read using NodeMcu8266
Important notes
According to the ESP8266 datasheet, the ADC pin has 10 bit resolution. This means that your analog reading will return a value between 0 to 1024.
The ADC only converts voltage between 0 and 3.3Volts. So before you apply any voltage to your A0 pin, you need to make sure that you’re using a device that only outputs 3.3V. Otherwise you might need to use a voltage divider: