Forums

Embedded Bluetooth module VS USB dongle

Started by Clint Sharp March 15, 2007
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.

My question is, would it be *much* easier to use a BT module than the 
dongle, I may want to be able to attach more storage in the future so I 
can log data outside the range of Blue tooth so the FTDI chip looks nice 
from the point of being able to attach a simple USB flash device as well 
although I could just attach an SD/MMC card to the PIC.

If the dongle route is 'do-able' Can anyone point me to any 
documentation that would give me an idea of what's involved in driving a 
USB Bluetooth dongle? In fact, even if it's not, I'd still like some 
kind of idea of what's involved even if I don't end up using the 
information straight away.

Obviously, if the USB dongle route is stupidly difficult compared to the 
oem module I'd be open to recommendations for a module with good code 
examples and/or good documentation.


Thanks in advance.
-- 
Clint Sharp
On Thu, 15 Mar 2007 19:00:04 +0000, Clint Sharp <clint@clintsmc.demon.co.uk> 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.
"Clint Sharp" <clint@clintsmc.demon.co.uk> wrote in message 
news:wMmE3OE0eZ+FFwJy@clintsmc.demon.co.uk...
> > 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. >
The Vinculum approach sounds cooler but if you want a BT-only recommendation I've tried the NSC LMX9830 UART/BT converter and it's very easy to use. https://www.national.com/ds/LM/LMX9830.pdf Andrew
"Clint Sharp" <clint@clintsmc.demon.co.uk> wrote in message
news:wMmE3OE0eZ+FFwJy@clintsmc.demon.co.uk...
> My question is, would it be *much* easier to use a BT module than the > dongle,
Yes. I use the modules from Ezurio (former TDK). These are controlled and configured by AT style modem commands. One configured (15 AT commands to be sent only once), these modules don't need any intervention from the controller anymore. The moment a PC or other BT host pairs to it, your serial channel is up. Meindert