Connecting sensors to your ESP8266 board
In this recipe, we are going to look at how to connect sensors to an ESP8266 board. There are two kinds of sensors that you will be using with your ESP8266: digital sensors and analog sensors.
The digital sensors output digital signals that you can read using the ESP8266 digital GPIO pins. The digital sensor outputs have only two states: high (logic 1) and low (logic 0). The high signals are ideally at a voltage level of 3.3V, while the low signals are at a voltage level of 0V.
Analog sensors output analog signals. The output comes in various voltage levels between 0V and 3.3V. The output signal is read using the ESP8266 analog pin (labeled ADC on our board).
It is advisable not to connect the analog sensor ...