A couple of weeks ago I was asked to write an assembly which should contain the necessary code for communicating with a payment terminal for a Point of Sale (POS) application. As you may have guessed from reading the title, the device in question is the Omni 3750 terminal. This terminal is produced by Verifone, check out the link if you require more information about this piece of hardware.

Although Verifone distributes this terminal in several countries supprisingly little can be found on the internet regarding communicating wih this device from any programming language whatsoever. The only thing I found was a rather short post on a Delphi forum. Together with some documents I received from the distributor of the Omni terminal here in Belgium this was enough to get me started.

This article concentrates on communicating with this device by using the SerialPort type and adhering to the required protocol. Hopefully this addition to the internet will save some people time in figuring this out.

Let’s get started…

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