68 ohm resistors

General discussions about V-USB, our firmware-only implementation of a low speed USB device on Atmel's AVR microcontrollers
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68 ohm resistors

Postby Guest » Tue Mar 27, 2007 7:04 am

Hi,

It says the 68 ohm resistors are not needed if there is a very short connection from the USB connector to the AVR.. I take it these are line terminating resistors, but any ideas on exactly where the value 68 came from, and if we can use different values? because 68ohm resistors are not very easy to get hold of for me..

Thanks

Grendel
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Postby Grendel » Thu Mar 29, 2007 2:41 am

I used 82 ohm resistors in my project w/o a problem.

Guest

Postby Guest » Thu Mar 29, 2007 6:24 am

Thanks. I suppose it is alot of factors that come into it, such as the length of the cable etc

christian
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Postby christian » Thu Mar 29, 2007 9:27 pm

The value is an "educated guess". Anything between 30 and 100 Ohms should work well enough.


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