The communication between the WiFi module and your microcontroller is performed by means of a standard asynchronous serial protocol. Almost all microcontrollers are equipped with at least one Universal Asynchronous Receiver Transmitter interface (UART), thus, the establishment of the communication is usually straightforward.
The serial protocol
The serial protocol is asynchronous and the bus consists of just three wires, the receiver line, RX, the transmitter line, TX, and the reference GND, as depicted in the following picture:
The serial protocol is usually configurable, thus, it is important to make sure that both devices on the serial bus are configured to use the exact same settings. In particular, to communicate with WiFi module the micro-controller's UART has to be set as follow:
- Data bits: 8
- Stop bits: 1
- Parity bits: 0
- Baud rate: 57600
- Flux control: None
The default baud rate of the Wi-Fi module is 57600 baud, but it can be changed both from APP (see module configuration) or through a serial command (see serial commands).
Logical Levels and Power Supply
Depending on the employed WiFi module, the power supply, and the electrical voltage on the bus, must be as follow:
- ESP-01 without adapter: 3.3 V
- ESP-01 with adapter ADP-01: 5 V
Please note that the power supply must be able to provide at least 300 mA