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Fast USB module from ACCES I/O packs 32 digital I/O lines

Posted: 24 Jun 2005 ?? ?Print Version ?Bookmark and Share

Keywords:ttl i/o? usb? universal serial bus? access i/o products? counter module?

If you need to add lots of TTL I/O capabilities to a USB (Universal Serial Bus) PC, check out ACCES I/O Products' ruggedized digital I/O and counter module. Priced starting at less than $120 a pop, the company's Model USB-DIO-32 is a true USB 2.0 high-speed device, but is also compatible with USB 1.1 systems.

Thanks to USB, this 3.5-by-3.7-inch unit is a plug-and-play peripheral. That permits hot connect or disconnect whenever you need additional TTL I/O to hang on your controller PC's USB port.

Independently selectable I/O

Once recognized by your host PC, the USB-DIO-32 gives you 32 lines of TTL-compatible digital I/O on four 8-bit ports with high-current output. The four 8-bit ports are independently selectable as inputs or outputs. All 32 buffered I/O lines provide the ability to sink up to 64mA and source up to 32mA. These I/O lines are driven by 74ABT245 three-state transceiver chips.

Optionally, this module also gives you three Intel 82C54-compatible counters. The three 82C54 chips pack three 16-bit counter/timers that are factory configured for use as event counters, frequency output, pulse width, and frequency measurement applications.

Each counter can be programmed to any count as low as 1 or 2, and up to 65,536, depending on the mode chosen. Modes include a squarewave generator, a software triggered strobe, and a hardware triggered strobe.

Power is typically supplied via a USB cable, but for higher-current applications, an external power option is available. Connections to the outside world are made using a removable screw-terminal adaptor. For external circuits, fused 5V is available at the connector. A re-settable fuse is rated at 0.5A.

The USB-DIO-32 is designed to be used in rugged industrial environments but is small enough to fit nicely onto any desk or testing station. The board inside is also PC/104-sized (more on that in a moment). The unit's electronics reside inside a steel powder-coated enclosure with an anti-skid bottom.

Windows driver

Unlike other USB digital I/O products that use USB's HID (human interface device) driver, this product uses a Windows-based custom function driver that's optimized for maximum data throughput. Also incorporated is a graphical setup program in Windows.

The USB-DIO-32 is supported for use in most operating systems and includes a free Linux and Windows 98-, Windows NT-, Windows 2000-, and Windows XP-compatible software package. This package contains sample programs and source code in VisualBASIC, Delphi, C++ Builder, and Visual C++ for Windows.

Third party support includes a Windows standard DLL (dynamic link library) interface that's usable from most popular application programs. Linux support consists of installation files and basic samples for programming from user level, via an open-source kernel driver.


There are also a number of options for the USB-DIO-32. For example, an economy version is available without the screw terminal adaptor. You can also order an OEM board-only version. The board's PC/104-compatible pre-drilled mounting holes ensure installation using standard standoffs inside most enclosures or systems.

- Alex Mendelsohn


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