That's kinda my point about using rs232. Serial to USB, serial to Ethernet adaptors will be available for a good long while.
Also why I like the idea of a standalone instrument that also has a pc interface of some sort. Or a slot for a pc interface of whatever source I want. So how does one build the core counter with a start, a stop, and maybe a 10 MHz reference input with sub 5ps resolution and accuracy? On Dec 19, 2010, at 3:50 PM, Bob Camp <[email protected]> wrote: > Hi > > The gotcha with caps is that they don't block RF very well. Of course if you > go high enough in frequency, not much can be blocked anyway. > > Opto isolated RS-232 is just a pair of cheap optos, a couple of diodes and a > few resistors and caps. It costs next to nothing and it will work just fine > for any speed you are likely to need in a counter. Spend $4 on a USB to > serial adapter and throw it away when the next generation of driver signing > (or what ever) renders it obsolete. Replace it with one that likely costs 50 > cents then. I won't go into the possibility that it might cost half a Euro or > $50 .... > > Bob > > > On Dec 19, 2010, at 12:01 PM, Poul-Henning Kamp wrote: > >> In message <[email protected]>, jimlux writes: >>> Bob Camp wrote: >> >>> There are some nice solutions, though, using USB directly, which has the >>> advantage of providing a few watts of power. Isolated DC/DC converters >>> are readily available. you might be able to do transformer isolation of >>> the two data wires. >> >> First: you want to use capacitors, not transformers. >> >> Second: it is surprisingly tricky to get to work in practice, I have >> only ever seen one device that managed to do so, and comply with >> the USB standard, and the designer swore to never do it again. >> >> People generally default to a small USB-enabled microcontroller >> with an optocoupler to the real stuff. >> >> -- >> Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 >> [email protected] | TCP/IP since RFC 956 >> FreeBSD committer | BSD since 4.3-tahoe >> Never attribute to malice what can adequately be explained by incompetence. >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
