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Application Notes - Putting the U401, U421, and U451 to work

The U401⁄U421⁄U451 can be used for a wide range of applications, tying devices to the PC via USB. It is very simple to interface to the U401 using it as a large SIP-type of device in your custom application. Using the U401 to interface with SimmSticks couldn't be easier. Like the U401, the U421 can also be used with solderless experimenter boards. The app notes located here in this section cover some of these potential applications.

All application files: (all application files)

Relays can be driven by the U401⁄U421 by setting the appropriate I⁄O lines to output and using appropriate relay driver circuitry. The Dontronics relay board DT205 is a simple way to accomplish this. The U451 has two on-board relays, and 6 open collector outputs that can be used to drive more relays.

Simple buttons, switches, and other CMOS-level inputs can be read by the U401⁄U421⁄U451. A Dontronics board, the DT203, can be used for input testing.

Many character LCD modules (HD44780 devices) are compatible with the LCD commands of the U401⁄U421⁄U451. These modules range from one row of eight characters to four rows of forty characters.

A serial shift device, such as the 74HC595, allows for the expansion of output lines via the SPI port.

A parallel to serial device, such as the 74HC165, will increase the number of input lines by shifting eight inputs in to the U401⁄U421⁄U451 via the SPI subsystem.

The U401⁄U421⁄U451 can be attached to a PC as a USB device and allow a circuit to use the 5V power from the USB port. There are examples of this in consumer devices, such as a notebook PC light.

A⁄D converters that interface via a SPI bus can be used to read analog values into the PC via the SPI subsystem of the U401⁄U421⁄U451.

Various microcontroller interface chips, such as some A⁄D converters, use a strobed read command to read eight bits of data. The strobe function of the U401⁄U421⁄U451 can interface to these chips.

SPI EEPROMS can be interfaced to the PC via the SPI subsytem of the U401⁄U421⁄U451. The EEPROM can be read and written using U401⁄U421⁄U451 commands.

The Atmel ATtiny series of microcontrollers can be programmed via the SPI subsystem of the U401⁄U421⁄U451.

SPI potentiometers can be interfaced to and controlled by the U401⁄U421⁄U451.

Door⁄window contacts can be monitored as inputs to the U401⁄U421⁄U451, and relays driven by outputs. Your home can be controlled by a PC interfaced to the U401⁄U421⁄U451. The U4x1 supports 1-wire⁄MicroLAN, often used in Home Automation for temperature sensing and remote I⁄O. The U451 with relays is especially suited to Home Automation.

Tethered robot experiments can be done with all of the features of the U401⁄U421⁄U451.

For more application information on interfacing components to I⁄O ports, check out books such as Jan Axelson's Parallel Port Complete and The Microcontroller Idea Book. The interfacing ideas in these books can be extended to the U401⁄U421⁄U451.

Hardware:  U401 USB Interface    U421 USB Interface   U451 USB Interface

Programming:  USBm DLL Programming    Download Files

Application Notes:  U4x1 Application Notes    Misc Applications and Information    FAQ

While every effort has been made to make sure that the information posted on this site is correct, the author can not be held liable for any damages whatsoever for losses as a result of the application of this information. Use this information at your own risk.

USBmicro can design your custom and semi-custom USB product. Email about USB design can be directed to " Robert " at

Copyright © USBmicro, L.L.C., 2002-2010

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