Bluetooth Serial communication between HC-08(Master) and HC-04(Slave)

This video show testing Bluetooth Serial communication between BT modules HC-08(in Master role) and HC-04(in Slave role). Seeeduino XIAO is programmed as USB-to-Serial bridge between host (Raspberry Pi in this example) and HC-08.

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Link:

~ Program Seeeduino XIAO as USB-to-Serial bridge

Program Seeeduino XIAO as USB-to-Serial bridge, to access HC-08 BLE 4.0 Module/ESP WiFi Modules.

HC-08 is a Bluetooth 4.0 low energy module. It provide TTL Serial interface. If we want to access it using PC, normal a USB-to-Serial adapter is used.

In this exercise, Seeeduino XIAO is programmed as a USB-to-Serial bridge to read/write HC-08 from Raspberry Pi using Arduino IDE's Serial Monitor.

Connection between Seeeduino XIAO and HC-08

XIAO		HC-08
=====================
3V3		VCC
GND		GND
TX		RX
RX		TX

For the code, simple foreward date from SerialUSB to Serial1, and foreward Serial1 to SerialUSB.

X_USBbridge.ino

/*
Xiao act as a bridge between USB and Serial device

It's assumed the device is running 3V3
Connection
Xiao Rx   - device Tx
Xiao Tx   - device Rx
XIAO GND  - device GND
XIAO 3V3  - device VCC

*/

void setup()
{
  pinMode(LED_BUILTIN, OUTPUT);
  
  delay(1000);
  SerialUSB.begin(9600);
  Serial1.begin(9600);

  //wait serial ports to device
  //while(SerialUSB);
  while(!Serial1);
  
  //Blink the LED 3 times to indicate program started
  for(int i=0; i<3; i++){
    digitalWrite(LED_BUILTIN, HIGH);
    delay(500);
    digitalWrite(LED_BUILTIN, LOW);
    delay(500);
  }
}

void loop()
{
  if(SerialUSB.available() > 0){
    Serial1.write(SerialUSB.read());
  }

  if(Serial1.available() > 0){
    SerialUSB.write(Serial1.read());
  }
}

This video show how it work.

Before HC-08 connected (LED blinking), You can read/write HC-08 status with AT Command.
After HC-08 connected with test app on Android phone (LED on), you can send/receive text to/from the app. 

To know where/how to download datasheet (with AT Command Set) and test app for HC-08, read the post "HC-08 Bluetooth Module (BLE 4.0)".

To install Seeeduino XIAO board to Arduino IDE, read the post "Seeeduino XIAO".

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This can be used to access HC-04 Dual Mode BLE SPP Bluetooth Module also.

Next:

~ Bluetooth Serial communication between HC-08(Master) and HC-04(Slave)

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Access ESP WiFi Modules:

With baud rate changed to 115200, it can access ESP WiFi modules. Tested with ESP-01S and ESP-12S.

X_USBbridge_115200.ino

/*
Xiao act as a bridge between USB and Serial device

It's assumed the device is running 3V3
Connection
Xiao Rx   - device Tx
Xiao Tx   - device Rx
XIAO GND  - device GND
XIAO 3V3  - device VCC

*/

void setup()
{
  pinMode(LED_BUILTIN, OUTPUT);
  
  delay(1000);
  SerialUSB.begin(115200);
  Serial1.begin(115200);

  //wait serial ports to device
  //while(SerialUSB);
  while(!Serial1);
  
  //Blink the LED 3 times to indicate program started
  for(int i=0; i<3; i++){
    digitalWrite(LED_BUILTIN, HIGH);
    delay(500);
    digitalWrite(LED_BUILTIN, LOW);
    delay(500);
  }
}

void loop()
{
  if(SerialUSB.available() > 0){
    Serial1.write(SerialUSB.read());
  }

  if(Serial1.available() > 0){
    SerialUSB.write(Serial1.read());
  }
}

Arduino IDE run on Raspberry Pi, to program Xiao as bridge to access ESP-01S:

HC-08/HC-04 Bluetooth Module

HC-08 Bluetooth Module (BLE 4.0)

HC-08 is a Bluetooth 4.0 low energy module, it can easily connect to iOS 5 and Android 4.3 or above by using a serial terminal app. You can use the Bluetooth communication up to 87 yards (80 meters) with this Bluetooth BLE module. It also runs on a 2.4GHz frequency. The chipset is CC2540 with 256K Byte space. You can change the role and serial baud rate and it supports AT commands for configuration.

It is very small in size, 1.1 x 0.5 in (26.9 x 13mm). The PCB thickness is 0.03 (0.7mm). Half-cut holes run along the lengths of the board, so it’s very easy to embed into your own project. It also has Tx and Rx 2.54 pin out, from which you can do a quick function test. Included are 90-degree male header pins.

HC-08 is a relatively new module made by an experienced Bluetooth design and manufacturing supplier in China. It’s mass produced and therefore well-tested. It can be incorporated into products or projects without worrying about being able to get it again. It’s already widely used in many Bluetooth projects.

Product page: http://www.hc01.com/products/6 (in Chinese)

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This video show how to download and run test app for HC-08 Bluetooth module, and also download datasheet with AT command set.

In the testing, a wire is used to connect between HC-08 TX and RX pins, such that the message sent will be echo back.

Summary of AT Command Set in the datasheet is captured here.

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HC-04 Dual Mode BLE SPP Bluetooth Module

HC-04 Bluetooth serial communication module is a new generation of dual-mode digital transmission module based on V2.1 (SPP) classic Bluetooth protocol and V4.0 (BLE) Bluetooth protocol. Only supports slave mode.

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Next:

- Program Seeeduino XIAO as USB-to-Serial bridge, to access HC-08 BLE 4.0 Module.

- Bluetooth Serial communication between HC-08(Master) and HC-04(Slave)