HC05 Connection Issue

Projects General Guidance
1

I am a teacher and we have a class set of Arduinos and Brainlink SE devices.

I followed an online tutorial to connect the device and arduino via an HC05. I set up the HC05 by putting it into AT mode and inputting the following settings:

  1. AT+UART=57600,0,0
  2. AT+ROLE=1
  3. AT+PSWD="0000"
  4. AT+CMODE=0
  5. AT+BIND=PUT-YOUR-MAC-ADDRESS-HERE
  6. AT+IAC=9E8B33
  7. AT+CLASS=0
  8. AT+INQM=1,9,48

Everything worked great for 10 of the 13 devices. These 10 had MAC addresses starting with 0D00. e.g. 0D00,18,A12CC9

The three that did not work were newer versions of the same device. They had MAC addresses starting with 4222. They do not seem to be picked up by the HC05 at all. It is not a communication issue, it is a connection issue. The HC05 does not blink slower when I turn on the device and it shows no sign of connecting to or recognising these devices.

When I connect them to the phone or a computer with bluetooth, all devices work exactly the same and will run various apps.

I have contacted the maker of these devices and they claim that there is no difference in how they have made the devices. The only difference was the charging port that is now USB-C.

I guess my question is, am I missing something obvious here? I have tested multiple HC05 chips, I have changed the devices, I have changed wires and Arduinos. Everything works with the older headsets but not with the new.

Is there another way I could format a MAC address than this?
AT+BIND=4222,22,266BAF

I can only think that the MAC address that I am using is not right...

2

I've seen reports where "newer" HC-05 batches were no longer capable of becoming master, just slaves.

Vendors do not seem to care in calling them still HC-05

(recent discussion in French here)

3

Thank you for this information. However, I do not think it is a HC-05 issue as all of my HC-05 chips work when connecting to the earlier versions of the BrainLink SE devices.

I am wondering if there is a change in bluetooth protocol on newer devices. Or if anyone could offer ideas on any tests I could do by changing AT instructions.

Is there an HC-05 alternative that would be recommended to test?