Revision 643eb9ec-b59a-419f-bd77-15691056d06c - Arduino Stack Exchange

I currently try to connect an Arduino Micro/Leonardo/32u4 to an ELM327 Bluetooth dongle using a HC-05 Bluetooth shield from iTeadStudio. I also have similar problems trying to connect to a bluetooth dongle (with added serial connection) on my PC.

The basic AT-command communication works, but I haven't found out yet why AT+PAIR or AT+LINK are failing and what should be done to avoid this (I've done dozens of Serial Monitor command iterations). Until now I haven't found a command sequence that reliably connects. What I've tried so far (from different documentation and example codes):

Check general AT command set:

 AT
 > OK
Reset to default values:

 AT+ORGL
 > OK
Set master mode and check it:

 AT+ROLE=1
 > OK
 AT+ROLE?
 > +ROLE:1
 > OK
Connect only to the specified bluetooth address:

 AT+CMODE=0
 > OK

Reset and initialize:

 AT+RESET
 > OK
 AT+INIT
 > OK
Configure inquiring mode:

 AT+INQM=1,9,48
 > OK
Inquire:

 AT+INQ
 > +INQ:12:34:567890:1F1F,7FFF
 > OK
 AT+STATE?
 > +STATE:INQUIRING

Try to stop inquiring:

 AT+INQC
 > OK
 AT+STATE?
 > +STATE:INQUIRING
 > OK
Reset and initialize again (otherwise we can't leave the inquiring state):

 AT+RESET
 > OK
 AT+INIT
 > OK
 AT+STATE?
 > +STATE:INITIALIZED
 > OK
Try to pair with the found device (my PC asks for the 1234-password and creates a serial port):

 AT+PAIR=12,34,567890,20
 > OK
 AT+STATE?
 > +STATE:PAIRED
Try to connect

 AT+BIND=12,34,567890
 > OK
 AT+LINK=12,34,567890
 > FAIL
 ...

Does someone have some hints for finding the right sequence?