You can get modules for both WiFi and Bluetooth that will connect to an embedded system through a UART interface, however a WiFi module will have far more processing power than your AVR microcontroller, often with spare capacity and I/O to execute additional user code, so connecting one to an AVR maybe somewhat redundant in many cases.

Bluetooth modules are simpler, less expensive, and the data-rate is better matched to the AVR s capabilities. For example these Parani modules. I have used them between an embedded system and a Laptop PC s Bluetooth, so given appropriate communications software, there is no technical reason why it could not be used with an iPhone I think. However this may be the flaw, on the PC the device was recognised as a virtual serial port, I don t know whether iPhone supports legacy communications in quite the same way.

For comparison, a WiFi solution

From what I know, BlueTooth is very limited on the iPhone: There is only very few BlueTooth-Profiles implemented, and - even if they can be extended with a jailbroken iPhone - I doubt this is easy to use from the application layer.

On the other side, transferring via WiFi requires a lot of processing power and memory since much more things have to be implemented before you can even start transferring data: 802.11, cdma/ca, arp, tcp. That s a big task.

Is it an option to build a hardware extension to the iPhone ? You might be able to get the serial connection and power out of the dock connector. Then even ZigBee could be very helpful.

Here s an article you might find helpful. I would lean toward a WiFi solution just because of the added flexibility available.

http://www.embedded.com/design/networking/215801088

-t

Some of the other people at the office have done AVR <- Bluetooth -> Symbian and AVR <- Bluetooth -> PC solutions without trouble. There is lots of info, reference designs and source available. I have no idea of how hard it would be to use Bluetooth on Iphone.

The exact module is probability also not important as long as it got some type of serial interface (I2C,SPI) to interface to the AVR and some source code show how to use the module.

Is it an 8-bit or 32-bit AVR? For the AVR32 processors there s support for WiFi in the Atmel 1.5.0 Software Framework using SD-card-mounted WiFi modules from HD Wireless (http://www.hd-wireless.se), including an IP stack (lwIP). Be aware that you need Ad-Hoc (IBSS) support to connect directly to the iPhone.

There is WiSnap kit. It can connect directly to a standard RS232 interface or through the TTL UART interface to embedded processors. We are planning to use it in our project. It also has Ad-Hoc support.

There are some usage examples and an iPhone application for connection setup.

http://serialio.com/products/mobile/wifi/WiSnapKit1.php

What are you trying to communicate between your AVR and the Iphone? The Iphone is made for the web along with everything apple (which AVR s are decidedly not). So what works well is an embedded device that exposes a web-interface. Like the Transmission bittorrent client on Linux. Also nowadays many low-power small form-factor linux platforms exist that will allow you to do this.

For instance Gumstix has an ARM based platform that runs linux and includes WiFi (Overo Fire).