HP 50g infrared transfer

[Martin Hepperle]

Hi Andreas,

indeed the HP 50g can send data to its IR-port using the IrDA protocol.
In contrast to the simpler HP 48G SIR protocol IrDA starts with a negotiation phase where both partners exchange information about baud rate etc.
This is part of a "discovery process" where the devices periodically send a message like "hello, I am here, who is there?" out into the blue until someone responds and a connection is established.
This type of communication is what you might have seen.

So the first question is: is your IR adapter really IrDA compliant and does it possibly need some software on the PC side to reply to the discovery messages?
The second question would be: did you use the "correct" baud rate, bit size and parity settings?

My Setup is as follows.

PC Side
An older Fujitsu-Siemens laptop S6010 with Windows XP. The IrDA port is an integral part of this system and uses a small window on the back of the computer.
Additionally I have installed the driver IrCOMM2K which redirects IrDA to a virtual COM port.
I use a terminal program such as Teraterm or Hyperterm to view the data. The baud rate setting in the terminal program seem to have no effect as the sped is controlled by the IrDA driver. I found no need to limit the transfer speed in the IrDA port settings of device manager.

HP 50g Side
Flag -34 set (use a serial protocol), flag -33 set (use the IR port).
Joe Horn also notes on his web site that flag -127 should be clear (IrDA and not SIR), but the Advanced Users Guide just tells the exiting story "not used" about this flag. I have to investigate this a bit more.

Operation
The HP 50g has to very close (approx. 20-40mm) and should have good batteries as the IR draws more current than regular operation.
Sometime the devices seem to have problems to establish a connection.

Baud rate settings seems to play no role as the speed is negotiated betwen the devices. I can print the stack or large RPL programs using the HP50g's print commands. If course the translation flag in IOPAR should be set to e.g. 3 to avoid "funny" characters on the receiving end.
For example I use <<OPENIO 5 WAIT PRST CLOSEIO>> to print the stack.

I am not sure whether the OPENIO / CLOSEIO is needed, but is does not hurt and I thought it might be good to WAIT some time to establish the connection.
DELAY can be zero and a BAUD rate in IOPAR of 115200 is possible. The transfer goes in chunks at high speed only the discovery and initiation of the connection can take several seconds.

Conclusions:
In general the communication works, but is a bit finicky to set up (distance, initiation of connection).

Martin