Issues with HC05

Projects Networking, Protocols, and Devices
1

Hello. I am a beginner to Arduino. I am currently trying to set up a simple circuit allowing control of an LED through interfacing with the HC05 module.

I have tried multiple iterations of this following several different tutorials but they are all having the same issue. For simplicity, I'm using the wiring and coding from the following tutorial for troubleshooting here:

My own coding and wiring:

char Incoming_value = 0;
void setup() {
Serial.begin(9600);
pinMode(13,OUTPUT);
}

void  loop() {
  if (Serial.available()  > 0)
    {
      Incoming_value = Serial.read();
      Serial.print(Incoming_value);
      Serial.print("/n");
      if (Incoming_value == '1')
        digitalWrite(13,HIGH);
      else if(Incoming_value == '0')
        digitalWrite(13,LOW);
    }
}

20240928_102225
20240928_1022251920×2560 396 KB

I am able to control the LED via input of '1' or '0' to the usb serial monitor, but I am unable to control it via Bluetooth apps. I am using "Serial Bluetooth Monitor" but I have also tried multiple other apps. I am able to connect fine to the HC05 device via bluetooth, but commands sent via the terminal on the bluetooth app don't appear to do anything.

I can only post three embedded items as a beginner but have pasted a couple of screenshots from the app configuration below.

Screenshot_20240928_103929_Serial Bluetooth Terminal
Screenshot_20240928_103929_Serial Bluetooth Terminal1080×2340 138 KB

Screenshot_20240928_103944_Serial Bluetooth Terminal
Screenshot_20240928_103944_Serial Bluetooth Terminal1080×2340 119 KB

I have tried switching out jumper cables. I have also tried with resistors in series on the LED.

If this helps, I read a little bit into the AT settings of the HC05 but didn't really understand. Currently the LED on my HC05 is blinking twice followed by a c. 5 second gap. The LED to indicate functioning of the TX/RX on my Arduino is not blinking at all.

Hope someone can assist.

2

Do not follow that Project Hub tutorial, as it gives very bad advice about connecting the Arduino and the HC-05. A logic level shifter is required when connecting 5V and 3.3V devices.

Unfortunately, you may already have damaged the HC-05.

This is a much better tutorial.
https://www.martyncurrey.com/arduino-with-hc-05-bluetooth-module-at-mode/

4

I am reading through this article now but a lot of it is beyond me. If the HC-05 is still functioning, does my project require that I have to enter the AT command mode to change settings in order to achieve this project? e.g. do I necessarily need to change the baud rate/whether it operates as slave/master?

5

The baud rates must match for any two devices communicating by UART serial.

Other serial device settings are usually standard, and for a project to simply control LED on/off, the serial baud rate is immaterial.

To get started with the HC-05, you must first communicate with it at the default serial baud rate. To learn what that is, check the docs for the particular HC-05 module you have. 9600 is typical.

7

No and No.
The Bluetooth Rx/Tx wiring you show is correct but it is good practice to have a 1k/2k divider in the Arduino Tx line and you really should have a series resistor with the LED. The Uno has a LED provided on pin 13 for this sort of thing and you would be better off using it.

Since you are using hardware serial, pins 0,1, and only use incoming signals, you can test things by disconnecting Bluetooth and using the keyboard instead