# Simple USB device

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#### Michael Searle

Is it possible to have a simple, dumb USB device?
All I want is latched digital IO and RS232 bridges - but everything USB is a microcontroller. I don't think a keyboard should need a 40MHz processor to control it... Am I just looking in the wrong places, or is USB just that fat?

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#### Wally aka skunk

Well, why not look at the big picture here ?
First to answer your questions, no, you can't just have a simple USB. Since USB has no central bus arbitration but for the and the computer, you can't just have your own device act differently. Sure , you don't need 40Mhz to run usb, but look at how cheap the solutions are. From $0.5 to about$5 apiece for usb solutions, why do something else ?
Another reason for needing a 40Mhz for USB may not
be the voracious need for computing power, but because of the serial nature of USB.
For all the megahertz talk, all usb needs is a 4 or 8 bit processor.
A solution for you if you are designing your own device may be to design one device with a microcontroller in it that will act like a hub, and then plug all your other devices into it.
For all the few bucks you may save, it may cost you more to debug a and test. Beside, US gives you the benefit and independence of wiring and a stable protocol for communications. Why mess around with it ?

Wally
http://www.embeddedwares.com

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#### Kim L. Ground

I recall recently seeing an ad from a company that makes USB boxes for developers to use as an interface device for their own hardware.
One of their products has 50 digital I/O. Other products have optoisolators or relays on the 50 I/O, and I think they also make a unit which has some serial capability. Unfortunately, this was not of immediate interest to me so I didn't save it, but I found it with a lycos search for 'USB'.