Difference between USB Modem and USB Dongle

Hi

Was just trying to implement bluetooth to my little project. Was reading Arduino Playground - Tutorial01, and realise the tutorial uses a Bluesmirf bluetooth modem on the arduino side and a bluetooth dongle on the computer side. I have this question in mind which I can't really find the answers around: What is the difference between the modem and the dongle? Can I simply replace the Bluesmirf modem with a USB Host Shield + USB Dongle on the arduino?

And has anyone tried the actual range of class 1 Bluetooth (despite them being stated to be able to reach 100m)?

Many thanks!

Can I simply replace the Bluesmirf modem with a USB Host Shield + USB Dongle on the arduino?

Yes, you can. As soon as you write the necessary code for the Arduino to talk to the USB dongle.

USB is a protocol that allows hardware to exchange data. The modem includes that hardware that makes the exchange of data possible, and the software to convert that data to serial data for the Arduino to read.

The dongle does not contain either the hardware or the software. The USB Host shield provides the hardware; you write the software.

Oh, and, no, it is NOT an easy task.

Spend the money and buy someone else's work.

Thanks for the reply.

Well my plan was to save some $$$ by using cheap USB Dongles, as compared to buying a Bluesmirf Modem or Xbees (incl 2 Xbee radios, Xbee Shield, Xbee Explorer Dongle).

Are there currently any libraries already written that allows USB dongles to be used on the USB Host Shield? I did manage to find one on http://www.circuitsathome.com/mcu/bluetooth-code-for-arduino-usb-host, but that seems still like a work in progress.

P.S. I'm trying to achieve a range of about 100 metres as well.

P.S. I'm trying to achieve a range of about 100 metres as well.

I think you need to look at the specs for bluetooth. Most bluetooth devices are class 2, with a limit of 10 meters.

Well i did see that the bluesmirf modem is a class 1 BT able to communicate at 100 metre range. But i wonder if that's really true? The environment which I am communicating is kinda open, from the ground to the air. Has anyone achieved 100m with bluesmirf or any bluetooth modems before?