After failed attempts and many computer reboots, I seem to have figured out how to use my Cingular 2125 (HTC Faraday) smartphone as a Bluetooth modem.  It seems you have to be aware of a few quirks to get it to work.  If you don’t follow the instructions exactly, you will get unhelpful error messages like “Connection failed.”

So, again, this applies to a Cingular 2125 Smartphone running Windows Mobile 5.0.  It also may apply to other Cingular smartphones.  It is also worth noting that this works with the Toshiba Bluetooth Stack for Windows.  At the time of this writing, you could find it here.  My friend Soren tried getting this working with the built-in Windows XP SP2 stack, and had different failures there.  In my experience it is somewhat easier to get this working over USB.  Here are some instructions that work for doing so.

So, let’s cut to the chase.  Here are some tips to help get your Smartphone working as a bluetooth modem.  First, look at the instruction manual on HTC’s site.  It is generally correct, but following it exactly didn’t work for me.

Quirk #1:

You need to specify the right GPRS access point.  I have the unlimited Media Net plan, which is one step down from the fancy full-IP-address plan, so I need to specify “wap.cingular” in the Advanced Initialization String.  If you have the full plan, I think you use “isp.cingular” here.  The manual also says to use the prefix “AT“, but in the case of the Toshiba Bluetooth stack, this is added for you behind the scenes!  So, drop the “AT“.

+CGDCONT=1,”IP”,”wap.cingular”

Quirk #2:

The phone number to use is *99#, however, I believe some other phones require *99***#1.  As a side-note, this number signifies that you want to use GPRS.  If you were trying to connect to a different ISP, you would use that here.  In that case, however, these instructions do not apply.

Quirk #4:

If at any point you disconnect the bluetooth connection abnormally, the phone must be rebooted or you will probably just get connection errors.