Chapter 12 Bluetooth Test

In earlier lessons, we explored wired serial communication. Yet, this approach is tethered to physical data cables, significantly constraining its potential use cases. Now, let’s delve into Bluetooth modules, which facilitate wireless communication. We’ll utilize a Bluetooth module to fetch commands from the Freenove APP and display them on the serial monitor.

Component Knowledge

Bluetooth

Bluetooth modules are devices designed for wireless communication, capable of transmitting data over short distances with the aim of facilitating low-power data transfer between devices. They rely on radio frequency signals, predominantly functioning in the 2.4 GHz band. This frequency spectrum is internationally recognized, ensuring compatibility and connectivity across various geographical locations.

The port description of the Bluetooth module is as follows:

Pin name	Description
STA	The pin indicates the connection status.
RX	The pin receives Bluetooth data.
TX	The pin sends Bluetooth data.
VCC(V)	Positive pole of power supply with voltage 3.3V
GND(G)	Negative pole of power supply

Steps of Bluetooth Communication

The process that the Bluetooth realize wireless communication can be simplified to the following steps:

Device Discovery

When the Bluetooth feature of a device is activated, it initiates a process known as “device discovery.” During this phase, the device broadcasts wireless signals to inquire if there are any nearby Bluetooth-enabled devices available for connection.

Devices Pairing

After identifying connectable devices, users must proceed with pairing. Pairing is akin to establishing a password for the devices, ensuring that only authorized devices can establish a connection.

Connection Establishment

Once the pairing is successfully completed, a connection is established between the devices. The Bluetooth protocol ensures that data can be transmitted smoothly. Bluetooth utilizes a technique known as “frequency hopping spread spectrum” (FHSS), rapidly switching between multiple frequencies, which reduces interference and enhances the stability of the connection.

Data Transmission

After the connection is established, devices can commence data exchange. Data is divided into packets and sent via wireless signals. The Bluetooth protocol manages these packets, ensuring they arrive at the receiving device intact and error-free.

Disconnecting

Once the data transmission is complete, devices can opt to disconnect. They will revert to the pairing mode, awaiting new connection requests.

Circuit

Correctly plug the Bluetooth module to the car.

Schematic

As shown in the schematic below, the RXD and TXD pins of the Bluetooth module connects Pico (W)’s GP0 and GP1.

Sketch

Open “Sketch_10.1_Bluetooth” folder in “Freenove_Omni_Wheel_Car_Kit_for_Raspberry_Pi_Pico\Four-Wheel\Sketches” and then double-click “Sketch_10.1_Bluetooth.ino”.

Code

/**********************************************************************
  Filename    : Sketch_10.1_BlueTooth
  Description : Use Raspberry Pi Pico Read the information received by 
                Bluetooth and print it on the serial port monitor
  Auther      : www.freenove.com
  Modification: 2024/08/23
**********************************************************************/

#include <Wire.h>
#include "SoftwareSerial.h"

SoftwareSerial bluetooth(1, 0);// Set pin TX to GP1 and pin RX to GP0

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);     // Set the baud rate of the serial port to 9600
  bluetooth.begin(115200);// Set the baud rate of the Bluetooth to 115200
  bluetooth.println("AT+NAME=BT05");  // Change Bluetooth device name
  delay(200);
}

void loop() {
  // put your main code here, to run repeatedly:
  if (bluetooth.available() > 0) {
    String message = bluetooth.readStringUntil('\n'); // Get the transmitted instruction
    Serial.println(message);
  }
}

Connection

Open Freenove APP and tap the omniwheel Car Kit.

If you have not installed the Freenove APP to your phone, please refer to Freenove app

Step 1: Click the connection icon on the left.

Step 2: Select the device named BT05. At this point, the blue indicator on the Bluetooth module blinks every one second, indicating it is waiting for pairing.

Step 3: When the connection icon turn blue and the indicator on the Bluetooth module blink rapidly, it indicates that the devices pair successfully.