Simple USB device


Thread Starter

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?

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 ?



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'.
Also most computer hardware places (Tiger Direct, Marlin P Jones, many others) sell USB devices which convert USB to standard serial or parallel port for less than $100. I don't know if one of the parallel port converters will let you individually control the parallel port signal lines like you can in a hardwired port or not, but if so this could be a low cost alternative if you need 14 or so i/o in the mix of i and o available on the standard parallel port.
Actually, yes you can there are two boards I've found recently on the internet. Both sell for around $50, include a preprogrammed controller chip with either the crystal on board or built in.
One provided 24 digital I/O lines. Follow this link
Or, this site that provides experimental boards, parts, and software to control 'your' device. The controller chip is an amazing $8.00.