HC - 05 AT command mode (Tutorial 2)

 

Hello everyone............

 

For basic info and communication mode of HC – 05 Bluetooth module visit Tutorial 1

 

HC-05 AT command mode:

 Follow the given steps to drive the Bluetooth module into AT mode.

 

1.     Power OFF the module i.e., disconnect supply voltage

 

2.     Connect KEY pin to HIGH.

 

3.     After a small delay (~100 ms), Power ON the module i.e., apply 5V supply

 

Now your module will enter into AT command mode.  Only if you again re-power the module with KEY pin LOW, your module will return to communication mode.

 

Please follow the steps correctly because most of the users face problems in entering AT mode.

 

After entering into AT mode, the module will be automatically set to 38400 by default (whetever be the baud rate in Communication mode). Hence the baud rate of serial communication should be set to 38400 (refer code).

 

Need for a relay circuit:

             For entering into AT mode, we need to cotrol the 5V supply voltage to the module. For this purpose I used a relay circuit board that I prepared myself. See this link for DIY simple relay circuit board.

 

Circuit Diagram:

           I have used GR-Sakura Board (Arduino Uno compatible).

 

 

 

 

Testing:

            If you send ‘AT‘, then you should receive ‘OK‘.

 

In AT mode you can configure the module settings such as name, baud rate (for communication mode), master/slave mode, change password, etc.

 

Example:

 

 

Code:

 #include <rxduino.h>

 

#include<iodefine_gcc63n.h>

 

int main()

 

{

 

  Serial.begin(38400);

 

  pinMode(2, OUTPUT);

 

  pinMode(3, OUTPUT);

 

  digitalWrite(3, 0); // switch off power supply to module

 

  digitalWrite(2, 0); // KEY pin of module LOW

 

  delay(1000);

 

  digitalWrite(2, 1); // KEY pin of module turned HIGH

 

  delay(100);  // a small delay

 

  digitalWrite(3, 1); // Switch ON Power supply to module

 

  delay(8000);

 

  Serial.println("Enter AT commands:");

 

  Serial1.begin(38400,SCI_SCI0P2x);  // pin20 and pin21 of sakura

 

  delay(100);

 

  while(1)

 

  {

 

              if (Serial.available())

 

              {

 

                          Serial1.write(Serial.read());

 

              }

 

               if (Serial1.available())

 

              {

 

                          Serial.write(Serial1.read());

 

              }

 

  }

 

}

 

 

 

Download the attached file for AT commands - HC-05 AT commands.