Re: Embedded Bluetooth module VS USB dongle

On Thu, 15 Mar 2007 19:00:04 +0000, Clint Sharp <clint@xxxxxxxxxxxxxxxxxxxx> wrote:

I'm currently running an embedded (OK, a small) PC that collects data
from the parallel port and sends them via bluetooth to a central
machine. I'm considering changing to a 'real' embedded device, partly
because I'd like the experience, partly because the power consumption of
the PC is too high for the job it does and mostly because it's too big.

The basic configuration I've sketched out on the back of the proverbial
envelope is a PIC 18F4550 (I'm already familiar with PICs and I've got
some of these chips) with an FTDI Vinculum chip hosting a USB Bluetooth
device because the Bluetooth USB dongles are considerably cheaper than
OEM Bluetooth dongles although all of the dongles I've pulled apart have
had a module fitted to a base board.

Check with FTDI to see if they support USB BT modules yet.... They didn't when I suggested it to
them last year.
In principle they ought to be able to, as, unlike many other USB devices, there is a well-defined
standard USB interface to the Bluetooth HCI layer so they shouldn't need any manufacturer-specifics.
However you probably want a layer or 2 above HCI, so you may need to implement this yourself.

This is where 'proper' OEM BT modules score in terms of ease of use. By the time you've added the
USB chip and surrounding bits, an OEM module isn't going to cost much more, but if the USB can have
other uses this may swing the decision.

I've used the The Bluegiga WT11/WT12, which have a nice ASCII wrappper interface, and the WT11 is a
Class 1 module - OEM modules don't often come in C1 versions.
The Bluegiga modules are a bit on the expensive side however.

These are the cheapest USB modules I've seen so far :
http://www.simplesolutions-uk.com/index.php?do=products&sub=list&group=42
Data :
http://www.simplesolutions-uk.com/datasheets/BT-20-HR_User%20Guide.pdf
Seem to be fairly profile-specific though.
.