How to setup HC05 Module to be distinguishable

Question

I'm not sure if this is a dumb question, but here goes 🤞 :

I am developing an Android app that uses a custom Bluetooth device as a companion. I'm using an HC05 module to interface the device with my app. What I need is a way for me to distinguish my HC05 module from, say, some other HC05 module that might be in range.

The obvious way of doing this would be to set the device name in a certain format. But I was wondering if there was a more better approach to this.

On searching, I found that UUID's are used for a similar purpose (i.e. service discovery), but I couldn't find any further info. Is it at all possible to set a custom UUID for the HC05 module so that I can filter devices in my Android app based on that?

Answer 1

Your options are:

1. As you guessed, you could set the name with AT+NAME=, and only use the names matching some pattern. It would work if you're only user so you just want to ignore other BT devices, but is problematic if you're having multiple independent users (each with its different set of *HC05*s) who might be in range (you could set different pattern for each user, though).

2. build a database of addresses (read-only with AT+ADDR?), and only access those devices that are belonging to that user. It would avoid problem above with multiple users, but would require some logistics on your part (for example, when you sell user the app and HC05s, in the registration process you'll need to assign exactly which HC05 address that user my access. Or you might want to allow user to pick which devices are his, by having him specify specify PIN for pairing set with AT+PSWD=)

3. third way is to use custom Inquire Access Code instead of GIAC so only that set of devices is scanned. HC05 allows setting it with AT+IAC=. However, as it is more complex and nonstandard that (2), and you'd probably still need to registration to differentiate which user is allowed which IAC, I'd recommend you do (2) instead.

Answer 2

As frarugi87 recommended in the comments, you need to change the device's name. Changing the device name will allow you to identify it by a custom name that you come up with. To do this you need to use something called AT Commands. Here is a guide that contains many of the system parameters that you can check and change via AT Commands: http://www.instructables.com/id/Modify-The-HC-05-Bluetooth-Module-Defaults-Using-A/?ALLSTEPS

Here is a brief summary about how to change the device name, quoted from the above Instructable:

First switch the device into command mode

For the HC-05 module to switch to AT command mode, the HC-05 pin 34 (often referred to as the Key pin) needs to pulled HIGH but in a certain order of events explained below. When the HC-05 enters the AT command mode, it will communicate at 38400 baud rate. Follow these steps in the stated order to switch to the HC-05 to AT command mode.

1. Wire the HC-05 and Arduino Uno per instructions.
2. BEFORE YOU CONNECT THE ARDUINO TO THE USB remove the VCC (power) red wire from the HC-05 so it's not getting any power from the Arduino. All other wires are still connected.
3. Now connect the Arduino Uno to the USB cable extended from your PC.
4. Make sure the HC-05 module is NOT PAIRED with any other Bluetooth device.
5. Re-connect the Arduino Uno 5V wire to the HC-05's VCC (5V power) pin.
6. The HC-05 LED will blink on and off at about 2 second intervals. Now the HC-05 is in AT command mode ready to accept commands to change configuration and settings.
7. To test if everything is wired correctly, open the Serial Monitor from the 8. Arduino IDE and type "AT" and click SEND. You should see an "OK" If you don't see an "OK" check your wiring.

Next run this program on your Arduino

/*

AUTHOR: Hazim Bitar (techbitar)
DATE: Aug 29, 2013
LICENSE: Public domain (use at your own risk)
CONTACT: techbitar at gmail dot com (techbitar.com)

*/


#include <SoftwareSerial.h>

SoftwareSerial BTSerial(10, 11); // RX | TX

void setup()
{
  pinMode(9, OUTPUT);  // this pin will pull the HC-05 pin 34 (key pin) HIGH to switch module to AT mode
  digitalWrite(9, HIGH);
  Serial.begin(9600);
  Serial.println("Enter AT commands:");
  BTSerial.begin(38400);  // HC-05 default speed in AT command more
}

void loop()
{

  // Keep reading from HC-05 and send to Arduino Serial Monitor
  if (BTSerial.available())
    Serial.write(BTSerial.read());

  // Keep reading from Arduino Serial Monitor and send to HC-05
  if (Serial.available())
    BTSerial.write(Serial.read());
}

Finally (the quotes aren't part of the command)

To change device name from the default HC-05 to let's say MYBLUE enter: "AT+NAME=MYBLUE"