Clock Question

Hang your monitor on the wall, and go to this web page:

Chris,

Writing the time to the serial port is not the problem. You need some kind of scheduling unless you want to synchronise your clock manualy every time. Running Linux it's easy. Can be done by a three or four line script starting a background process. Windows has its own scheduler(s) although I can't imagine a simple script to run it a the moment. As DOS lacks multi tasking, writing a scheduler is not that easy. It nervertheless can be done if you make it a device driver or another resident program. Unless you're running Linux it's much easier to do the scheduling by the clock itself. Make it send a kind of a signal to the computer using the serial port. This signal activates an interrupt routine that replies by sending the system time.

petrus

...

Make a cron job that outputs the time 12.00pm (midnight) every sunday:

crontab -e

• * * * 0 date > /dev/ttyS0

"date" can put out many formats, so you can suit it to the format parser in the clock.

Get a WWVB clock. Radio Shack, among many, sell them. You can get them for $25 to $80 depending on options. The WWVB clock probably has better accuracy than SNTP, especially if your using XP (XP has big problems with SNTP).

If you really want to get silly, you can find these GPS synchronized HP boxes (e.g. model Z3801)on Ebay. They provide an accurate 10 MHz reference (less than a ppb) and very accurate time. Require a few days to settle in.

Mark

Use preset counters to store the time. Then every 24 hours have your computer send a single bit to trigger a reset of the counters. Works best if you do a reset a 23:59:59 hrs . Details of the clock flipflop/counter network not available at printing. ;)

Charles

Use NTP to sync them together. Free, simple, built into the OS.

Set up one of the machines as the NTP master. Use one of the several available utilities to sync it to WWV via RF, dialup, or internet. Still free (assuming internet connectivity.)

Good idea. I strongly think it will work.

To illustrate your obsession outside the lab, you need your own "atomic clock wristwatch":

This is the Real Deal, not a wimpy WWVB watch!

Tim.

I've gotten this brand of logic from many people over the years, Jim. Don't listen. My first self-setting clock was the Heathkit Most Accurate Clock, a-way back in the 80's. Most people who saw it were not impressed: "Whaddya need that kind of accuracy for??" was the usual response. Well, I confess I _am_ a clock bigot - have been since my time in the A.F. back in the 60's when I was responsible for our H.P. cesium beam-driven world time clock - but I didn't get the Heath clock because of a necessity for split second accuracy. I got it because it was cool.

After studying the Heath clock's schema for upteen months I decided I could do it better and cheaper. I had to learn microcontrollers first, chose the Z80B because it was readily available, cheap, and a freeware assembler was available. That whetted my appetite, set me to learning an ancient Motorola NMOS chip. And that's what I used for my clock. I built it in 1994 and it's been running ever since.

No, we don't need split-second accuracy. That comes as gravy from a box that doesn't need resetting even when the bad ol' spring-ahead-fall-back disruptions occur. That's what I love, not having to reset my clocks several times/year simply because some doofus decided that the sun gets out of whack WRT the correct - read "human" - biorhythm.

Tom Gross wrote: (snip)

WWV? Or should that have been "WWVB"?

I've said several times, "This is for fun and pizzazz".

Of course one thing that will NEVER happen is that I would own an Impala... sheeeeesh, that's a GM product... I've haven't owned an American automobile since 1977 when I gave up on Ford ;-)

...Jim Thompson

yes, I will have to set up one of the XP Pro machines as a master time server. I can't rely on any of my machines actually being connected to the web (in this application) but it's really not that important to me, as long as they think it's the same time down to about a second.

Apparently the two homebrewed machines I have with ASUS motherboards are consistently running too fast, gaining about 15 seconds per hour.

With all the "Buy American" hoopla currently extant, it would be interesting to poll how many American engineers drive American cars. I haven't owned one in decades.

Bob

That's certainly true, I was only really replying to the specifics of DOS output. Personally as I start the pc every day I would probably just put it in the autoexec to sync once per day, or use 98's task scheduler to call a batch file. Messy though. My other approach would be to write something in Delphi (or possibly Visual C for the challenge) that would work as you suggest.

My linux skills are a long way short of scripting this sort of thing!

Or you could do the following command (at least it works on my Win98 and XP machines):

echo. |time

That's the pipe character before time, and don't leave out the period. It pipes the carriage return produced by the "echo." command into the time command.

Set up a job in Scheduled Tasks (the task GET_TIME executes TIME_IS.BAT hourly).

Carl D. Smith

:: TIME_IS.BAT writes the current time to the serial port. @echo. | TIME | FIND "is" > COM1: (One executable line; auto-deletes the temp file.)

I think that's what I was looking for when I set out to refresh myu mind on redirection! Thanks for the reminder Carl.

That's a shameful photo - there's some clear space which could be usefully filled! :-)

Ken