Understanding Phidgets

Hardware Model

All Phidgets are connected to the computer using USB. Most computers support up to 127 USB devices (or more), so it is easy to connect as many Phidgets as are required for almost any project. Phidgets can be connected either directly to a computer or through Hubs, but there are some limitations.

The maximum cable length for USB is 15 feet. This is a maximum distance between device and computer, even if there are one or more Hubs in between. There are cable extenders available on the market, but these can be unreliable and are not endorsed by Phidgets Inc. Users should never try to run USB over anything other then a certified USB cable, and should never try to run it longer than the spec.

Phidgets run as USB 1.1 low speed or full speed devices, and are supported by both USB 1.1 and USB 2.0 hosts.

Software Model

The Phidgets Labview library is written under the C library - phidget21, which implements the low-level protocols necessary to communicate with the Phidgets, and exports a unified interface to the software programmer. This also makes the Phidgets Labview library cross-platform.

The Phidget Labview library contains only glue logic for interfacing with the C library, thus making maintenance much easier. It should be noted the library employs threading and events extensively. (See Programming Concept for more information.)