I would like to determine the format for the serial protocol between a Dallas SemiConductor Ibutton and a pc.

We bought this technology from a healthcare company. The IButton allows us to transfer data from a piece of medical equipment into a a pc based database. The IButton is touched to a probe on the machine, data is tranferred to the button. The button is then touched to a probe on the pc and the data is loaded onto the pc.

This works fine except that the healthcare company no longer supports the database and to top it off they contracted out the implementation of the iButton technology from a firm that is now out of business. The IButton technology is owned by Dallas semiconductor, but their documentation of the button is very low level (hardware) and not helpful to a software developer.

I would like to somehow "sniff" the serial cable to determine how write a routine to transfer data from the button to a pc. Any ideas on how I could eavesdrop the serial cable?

I don't think I am infringing on anyone's trade secrets. Comments appreciated.