Test Bluetooth on ESP32

Components

In this experiment, we need to use a Bluetooth dabbed serial Bluetooth terminal for a study. If you haven’t install it, please click the installation: https://www.appsapk.com/serial-bluetooth-terminal/ .

Here is its sign:

Component Knowledge

Bluetooth is a short-distance communication system that can be divided into two types, namely low power Bluetooth (BLE) and classic Bluetooth. There are two modes for simple data transfer: master mode and slave mode.

Master Mode:

In this mode, work is done on the master device and can be connected to the slave device. When the device initiates a connection request in the main mode, information such as the address and pairing password of other Bluetooth devices are required. Once paired, you can connect directly to them.

Slave Mode:

A Bluetooth module in the slave mode can only accept connection requests from the host, but cannot initiate connection requests. After being connected to a host device, it can send and receive data through the host device. Bluetooth devices can interact with each other, when they interact, the Bluetooth device in the main mode searches for nearby devices. While a connection is established, they can exchange data. For example, when a mobile phone exchanges data with ESP32, the mobile phone is usually in master mode and the ESP32 is in slave mode.

Wiring Diagram

We can use a USB cable to connect ESP32 mainboard to the USB port on a computer.

Test Code

//**********************************************************************************
/*
 * Description : ESP32 communicates with the phone by bluetooth and print phone's data via a serial port
 * Auther      : http//www.keyestudio.com
*/
#include "BluetoothSerial.h"

BluetoothSerial SerialBT;
String buffer;
void setup() {
  Serial.begin(115200);
  SerialBT.begin("ESP32test"); //Bluetooth device name
  Serial.println("\nThe device started, now you can pair it with bluetooth!");
}

void loop() {
  if (Serial.available()) {
    SerialBT.write(Serial.read());
  }
  if (SerialBT.available()) {
    Serial.write(SerialBT.read());
  }
  delay(20);
}
//**********************************************************************************

Test Result

Compile and upload the code to the ESP32. After uploading successfully，we will use a USB cable to power on. Open the serial monitor and set the baud rate to 115200. When you see the serial prints the character, as shown below, it means that the ESP32’s bluetooth is waiting for connect ion with a phone. (If open the serial monitor and set the baud rate to 115200, the information is not displayed, please press the RESET button of the ESP32)

Ensure that your mobile phone Bluetooth is enabled and the Bluetooth application of “Serial Bluetooth Terminal” is installed.

Click“Search”，search for the nearby Bluetooth and select to connect the“ESP32 test”.

Open the software APP and click the left side of the terminal, select “Devices”.

If you select ESP32test in classic bluetooth mode, a successful connection message will appear as shown below.

Data can be transferred between your phone and a computer via ESP32 now.

Send “Hello！”, When the computer receives it, which will reply with “Hi!”.