I think it may be the voltage. Do the USB converts use rs232 levels or only 5 volts?
For NTP the issue is different. The PPS signal coming from the GPS needs to go into a hardware serial port so the PPS handler sees a very low but more importantly a predictable latency. The PPS depends on a very specif interface to the hardware interrupt controller. On Mon, Jun 13, 2011 at 3:25 PM, Alan Melia <[email protected]> wrote: > This is raising an interesting point, only vaguely relevant, but we have > been > testing some software for amateur radio astronomy purposes that controls > intruments over serial lines RS-232 or RS-485. Whilst many application run > with out problems for days on internal serial cards, we seem unable to find > any USB to serial converter that performs anywhere near as well.on our > loopback tests. Many of the fail rates suggest that slower speeds give a > longer period between errors, but with one well-known converter we could not > run at all at 57.6kB. This may not be too much of a problem with GPS control > program speeds but it would seem there are few totally reliable products. It > may be much more serious for NTP operations. > > Of the USB converters the best seemed to use the FTDI chip and driver, but > even > these have shown fails suggesting the problem is deeper inside the PC. All > problems have been on the PC reception leg, causing corruption, and often > what seemed like a driver disconnection so the "serial port" became > disconnected from the application, and required the app restarting. > > Alan G3NYK > > ----- Original Message ----- > From: "David VanHorn" <[email protected]> > To: "Discussion of precise time and frequency measurement" > <[email protected]> > Sent: Monday, June 13, 2011 10:46 PM > Subject: Re: [time-nuts] Advice on NTP server needed > > >> >> ________________________________________ >> >> >> Unfortunately, my D525 mobo doesn't have a serial port and my symetricom >> doesn't like the usb converter. One of these days somebody is going to >> make a usb coverter that really looks like a serial port. I'm probably >> going to buy a serial card for the box if all else fails. >> >> >> >> The best serial port boxes I have found, are Edgeports. They are > available in 1/2/4/8/16 port versions, and I've picked up the 8 port > versions for $50 on ebay. >> Dead solid, and reliable. I haven't hit anything that wouldn't work with > them. >> _______________________________________________ >> 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. > -- Chris Albertson Redondo Beach, California _______________________________________________ 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.
