Palm IR interfacing

Palm uses the IrDA protocol, which can be downloaded from:

For Windows, there is a wide range of serial-IrDA or USB-IrDA adapters, but all require a Windows driver to operate; I believe several are supported by Linux.

Actisys sells a complete embedded solution, which consists of a chip that implements most of the IrDA stack, and communicates over a serial port to your microcontroller.

Note that IrDA devices fall into two categories, Primary ("host", generally a PC) amd Secondary ("slave", generally a PDA). If you want to communicate with an existing PDA, you will need to implement a Primary device, which is typically more work.

Note also that single-chip solutions as described only implement the physical and network layer; that is, they can send and receive packets reliably, but can't perform the higher application layer functions, which is where most of the automation of IrDA comes in: recognizing the type of data being received, and how to manage it (usually implemented using IR Object Exchange, or "IrOBEX").

--Gene

The protocol is IrDA.

Microchip have a single chip solution which implements all the lower layers of the protocol, up to and including IrComm. Microchip MCP2155, AFAIR. It will auto-connect when in range and establish a virtual COM port serial link to the Palm. I have used this before; it works nicely.

Thanks to Gene and Matthew for the pointers. The spec is a bit rich at $490 for the "set". I'll see if I can get the info another way, or I could use one of the interface chips. I was hoping to just roll the spec into the MCU I will be using anyway. Seem silly to put two chips on a simple board like this.

I see that the MCP2155 has signals for the MCU (DCE) side of the interface that include all the modem handshake signals like ring indicator. Does the protocol simply emulate a UART interface on each side like the Bluetooth interfaces typically do for GPS receivers? Are all of the modem control lines availble for handshaking?

Hmm, that's funny. I'm pretty sure the specs used to be available as a free download from irda.org...

--Gene

There is a book "PDA Robotics" which covers IrDA and the Palm.

Don

Yes. On the Palm your software simply opens a serial connection, specifying the IrDA virtual COM port rather than the physical serial port. It can then talk to the remote device in exactly the same way as if it were connected directly. I don't remember the details but it was pretty straightforward under Palm OS.

On the other end of the link the MCP2155 provides a full set of (logic level) RS232 signals, emulating a UART. You would typically connect these to a UART interface on your microcontroller.

Like Gene, I also remember the IrDA specification used to be a free download. In any case, you probably do not want to have to implement this yourself. It is a fairly complicated multi-layer protocol and unless your project is very cost sensitive it is probably better to use a dedicated interface chip that does it for you.

Another Microchip solution is the PIC24. Its UARTs support IrDA, and Microchip has a free IrDA stack that runs on the PIC24.

--
John W. Temples, III

There are free IrDA stacks (only 9600 baud) for 8051 and other processors

and there are some home projects on the internet ( I had a short list but I can't find it right now).

Here is a good place to start. I'm not sure if you will be able to find the spec for free though.

or

Thomas