"Robert Rolf" wrote: > Then you are NOT isolating USB, are you? You are isolating > a MUCH slower serial signal. Perhaps I didn't follow the thread closely enough. I thought Morgan only wanted a substitute for an isolated serial port. I didn't think full speed USB was required. Technically, the USB is not isolated from the PC, only the circuitry on the other side of the optocouplers. Putting the USB circuitry in its own isolated area of the PWB and powered via the USB port should fit the original intentions. . > Or you could use damn fast opto's like those that HP optical make > (whatever they're called now) and USB transceivers to get to/from > differential drive. Actually, I used Fairchild H11L1xxx parts. As I recall, they were good for about a 1MHz signaling rate and had schmitt trigger outputs. I used the word "optocoupler" rather generically as I feel everyone is familiar with the term. Not that I used them anywhere near their rated speed. The advantage of going the FT232BM and opto route is that it was a "no brainer" design. Also a "one-of" design (no need to optimize cost at expense of development time). Ken klumia@adelphia.net ----- Original Message ----- From: "Robert Rolf" To: "Microcontroller discussion list - Public." Sent: Friday, October 01, 2004 2:15 PM Subject: Re: [PIC] ICD 2 clones - The Empire Strikes Back? USB isolation > Kenneth Lumia wrote: > > "Morgan Olsson" wrote: > >>Serialports is possible and easy to optoisolate. > >>For the current project i can not use USB in final test as the PIC > > cirquitry is on high voltage. > > > > Actually, it is relatively simple and not much more expensive to isolate the > > USB > > port. I did this on a project for a Circuit Cellar competition and it > > proved > > rather easy. Take your USB and use a FT232BM chip to convert USB > > to serial. Add 2 optocouplers for TX and RX and connect the other side > > Then you are NOT isolating USB, are you? You are isolating > a MUCH slower serial signal. By that reasoning you could use > Ethernet<=>USB modules and call it 'isolating USB'. > > > to the projects serial port. In my case, it was an AVR, however a > > PIC would be similarly wired. If you lay it out correctly, the worst > > case isolation is the optocouplers rating. > > Or you could use damn fast opto's like those that HP optical make > (whatever they're called now) and USB transceivers to get to/from > differential drive. > > Robert > _______________________________________________ > http://www.piclist.com > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > _______________________________________________ http://www.piclist.com View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist