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CWAV's low-cost USB pod turns PC into scope, logic analyzer

Posted: 03 Oct 2005 ?? ?Print Version ?Bookmark and Share

Keywords:cwav? usbee? zx digital test pod?

USBee AX Test Pod

Back in 2003 I covered one of CWAV's first products, the USBee ZX Digital Test Pod. Using high-speed USB, the pod provided an assortment of digital test and control functions on a PC. It could work as a logic analyzer, signal generator, datalogger, pulse and frequency counter, serial controller, a PWM (pulse-width modulation) controller and more.

CWAV supported the ZX with its USBee ZX Toolbuilder software that let you create custom test tools using VisualBASIC or C++. CWAV supplies source code in its top of the line model.

Like the USBee ZX Digital Test Pod, the new USBee AX Test Pod leverages the speed of USB 2.0 to stream data to and from your PC. This endows the PC with all necessary triggering functions, as well as permitting data storage. The pod also derives its operating power from the bus, so no external supplies or bricks are required.

To run the newest pod, your Pentium PC needs to be equipped with Windows XP or Windows 2000, and have a USB 2.0-enabled port. You'll also need at least 32MB of RAM and 125MB of free disk space. Internet access is required so that you can get software updates.

A variety of test gear
Like the USBee ZX Digital Test Pod, the USBee AX Test Pod can also function as a wide variety of test equipment. You can use it as an I?C decoder just as easily as a digital voltmeter or a signal generator. Depending on model, and price, it offers quite a versatile mix of functions.

As an oscilloscope, the USBee AX Test Pod offers two 3MHz analog bandwidth high-Z input channels that can run at a maximum analog sample rate of 12MS/s, yielding 256 steps of analog resolution. Inputs can span 10V in amplitude. Like a conventional scope, the system's volts/division settings span 100mV to 5V in six steps. Likewise, the time/division sweep settings span 100ns to 2s in 23 steps.

The scope mode's triggering include settings that you'd expect on a benchtop scope. Included are Auto, Normal and Single trigger modes, for example, and you can establish the tirgger position on a waveform.

As a logic analyzer, the USBee AX Test Pod gives you eight digital channels, and operates at a maximum sample rate of 24MS/s, with either internal or external clocking and four trigger levels.

Trigger qualifiers can be set on a rising or falling edge, or on a high or low logic level. The system accommodates sample rates from 1MS/s to 24MS/s.

Mixed-signal analysis
Significantly, the pod can also work as a mixed-signal scope, combining the attributes of analog oscilloscope functions and logic analysis.

What's more, CWAV claims its approach pushes sample storage way beyond that of dedicated oscilloscopes and logic analyzers. In use, the USBee AX Test Pod uses the PC's memory as a sample buffer, supporting selectable sample depths from one to many hundreds of millions of samples. That complements the pod's ability to both capture and generate samples up to a maximum rate of 24MS/s (depending on PC configuration).

The USBee AX also uses a unique auto-calibration feature. It automatically reduces the sample rate to ensure accurate and reliable timing, even on PCs with slower microprocessor and USB speeds.

Finally, CWAV supports its products with a raft of free software and source code listing downloads, manuals, and AVI tutorials on its Web site. However, the USBee AX is not yet covered at this time, but that's expected to change shortly.

- Alex Mendelsohn

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