Bluetooth: HC-05 or HC-06?


We encounter some difficulties using a Bluetooth V2.0 Serial Transceiver Module - 3.3V (SKU: 800133001), which corresponds to a HC-05 model (master/slave). … -1731.html

From what we observe, it seems to behave like a HC-06 (slave or master only), which is visually identical, but has a different pin usage & a different communication protocol, along with a drastically reduced set of commands.
  • It does not understand the command “AT\r\n”, but answers to a simple “AT” with a bare “OK”, without “\r\n” either. The documentation states: «HC-03 and HC-05’s command should end up with “\r\n”. It means when you finish programming, you should add terminator (“ENTER” or “0x0d 0x0a”) to the program. It’s different from HC-04 and HC-06 (They don’t need terminator).»

  • The only other two commands it responds to are: “AT+PIN1234” (“OKsetPIN”) & “AT+BAUD4” (“OK9600”), always without “\r\n”. The HC-05 is supposed to know many more instructions, such as: RESET, VERSION, etc.

  • We get a square signal on PIN24 (LES for HC-06) with a period of 220ms. The documentation tells about a 110ms period, for the master device. But if it were a master, shouldn’t it understand more commands?

    We have contacted Seeed Studio customer service three weeks ago, to find out if there had been a mistake in the shipment, but haven’t got any reply. We have ordered the same module (same reference) from one of their distributors, and we get exactly the same results from it. So we wonder if there is something we missed in the use or configuration…

    How can we be sure of which version is the module: HC-05, HC-06(slave) or HC-06(master)?
    If it is indeed a HC-05, why does it miss the “\r\n” part & not answer the commands? How can we communicate with it to set master mode?
    It it is a HC-06, how come two sellers have made the same mistake? How & where can we order the HC-05 and be sure that they will send us what we asked for?

Thank you for your help.