I design in asynchronous serial for diagnostics all of the time. It is easy to galvanically isolate if necessary, is easy to debug, uses the fewest pins, and is well supported on both ends although if needed, USB to serial translation always seems to cause more problems than it solves. I do not remember now where I saw it but many years ago, I ran across an RS-232 type of interface where the first edge of the start bit was used as the high precision timing reference for the following message. I am not sure of the exact details but as I recall, the UART had some external glue logic and maybe a synchronous clock so the start bit edge was aligned to the timing reference to within the inherent jitter of the glue logic without any clock uncertainty. The receiver had a standard UART with a parallel low jitter logic path to watch for the start bit. On Wed, 10 Oct 2012 11:49:13 -0400, "Bob Camp" <lists@rtty.us> wrote: >Hi > >If they had done USB instead of HPIB / GPIB, a lot of the drivers would have >been "out of service" by the time Windows 95 came along. No chance at all of >them working under Windows 7. > >For the complexity, it'd have been better if they used something more like >Ethernet. Except in 1968, you would have set up for something other than >TCP-IP. Anybody running a Token Ring network in the basement? > >No easy solution. Serial com is still with us because it's a lowest common >denominator. I'm sitting here coding it into a new product right now (once >the uber super compiler finishes a build). It's supported on just about >every chip set in the universe. I suspect it will outlive the cockroaches. > >Bob > >-----Original Message----- >From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On >Behalf Of David >Sent: Wednesday, October 10, 2012 10:54 AM >To: Discussion of precise time and frequency measurement >Subject: Re: [time-nuts] 57600 baud rate with Basic etc > >What aspects of USB would HP have used? Just the complexity of a USB >OHCI/UHCI would have been economically prohibitive compared to an >asynchronous serial UART. An OHCI/UHCI is more like an ethernet >controller and those took up the space of entire expansion boards >initially. > >What they did come up with was HP-IB although I would have preferred >it to be serial and galvanically isolated. > >On Wed, 10 Oct 2012 10:28:46 -0400, paul swed <paulswedb@gmail.com> >wrote: > >>I have never figured out why HP did not develop USB in 1969? Not very far >>sighted. ;-) >>Regards >>Paul >>WB8TSL

Most computers and RS-232 interface chips made in the last 10 years support 0-5V as well as +/- 12V. Didier KO4BB Sent from my Droid Razr 4G LTE wireless tracker. -----Original Message----- From: Bob Camp <lists@rtty.us> To: 'Discussion of precise time and frequency measurement' <time-nuts@febo.com> Sent: Wed, 10 Oct 2012 11:09 AM Subject: Re: [time-nuts] 57600 baud rate with Basic etc Hi Again, I'd say it's the lowest common denominator. Synchronous comm using RS-232 levels on a DB-25 came before asynchronous comm. It's long dead. Being first isn't *always* best. Same could be said of 125V / 60 ma current loops. I suspect serial will easily outlive RS-232 levels though. Bob -----Original Message----- From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On Behalf Of Michael Tharp Sent: Wednesday, October 10, 2012 11:55 AM To: time-nuts@febo.com Subject: Re: [time-nuts] 57600 baud rate with Basic etc On 10/10/2012 11:49 AM, Bob Camp wrote: > No easy solution. Serial com is still with us because it's a lowest common > denominator. I'm sitting here coding it into a new product right now (once > the uber super compiler finishes a build). It's supported on just about > every chip set in the universe. I suspect it will outlive the cockroaches. Basic serial has its merits, but it's regrettable that RS-232 came out on top. RS-422 (or full-duplex RS-485, not much difference) would have been a much better choice. Differential so it has good noise resistance, and it doesn't use weird voltages (-12V? come on...) It all looks the same from the software side though. Bytes in, bytes out. -- m. tharp _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.