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Discussion Starter #1
So, I'm building a clock.

IMG_20140915_222238.jpg

That's an Arduino Yun, a DS3232 thermocompensated RTC, and a display module. It's kind of working now, in that the display is reading from the RTC which was set from NTP off the internet... but not working with great precision yet, as the interrupts are not hooked up. It should be around 20s/year right now, but I'm hoping for much better than that.
 

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Discussion Starter #3
I don't know yet... I might. It has been fairly straightforward as soldering goes... but the next feature won't be.

I'm working on outputting JJY and WWV time code. The analog output for that is going to be somewhat annoying to build.
 

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I don't know yet... I might. It has been fairly straightforward as soldering goes... but the next feature won't be.

I'm working on outputting JJY and WWV time code. The analog output for that is going to be somewhat annoying to build.
This really does fill a big gap in the HAQ world. I don't think there has ever been a TC clock, so I wish you the best of luck with this.

It won't be of great interest to you on the other side of the world, but you might care to add MSF and DCF77 while you're at it.

The next request will almost certainly be from someone demanding a wrist shot. :)
 

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This really does fill a big gap in the HAQ world. I don't think there has ever been a TC clock, so I wish you the best of luck with this.

It won't be of great interest to you on the other side of the world, but you might care to add MSF and DCF77 while you're at it.

The next request will almost certainly be from someone demanding a wrist shot. :)
Too many initial requests might diminish the chances of it being available to us.
 

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Discussion Starter #7
More likely, will result in incomplete firmware with extras left as an exercise.

DCF77 needs a differently tuned output stage, so that's definitely going to take a while if it ever happens. MSF is no big deal, just another modulation.
 

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More likely, will result in incomplete firmware with extras left as an exercise.

DCF77 needs a differently tuned output stage, so that's definitely going to take a while if it ever happens. MSF is no big deal, just another modulation.
Sure. Just thought you'd like to have a few features on your to-do list, in case you get bored. Don't forget the perpetual calendar when you are adding extra digits to the display.
 

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Discussion Starter #9
Sure. Just thought you'd like to have a few features on your to-do list, in case you get bored. Don't forget the perpetual calendar when you are adding extra digits to the display.
There's a perpetual calendar mode already... have to connect to the device with ssh from a computer to select it, but the calendar is there and working :)
 

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Um... not no time at all, I'd have to write code for all of those, whereas the calendar is a hardware feature. Tourbillion... er, no.
I guess I'll be able to live with my disappointment if you can achieve the basic item. Selling a kit of parts (let alone an assembled clock) may be a bit of a stretch, but I'm sure there would be a few here who can manage a soldering iron without too much personal injury and would welcome the opportunity to build their own from your specification.
 

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Discussion Starter #14
Well, I'll take that as interest in a productised version at some time.

One of the nice things about this architecture is that many crazy complications are really easy on the linux side, and that CPU can use the display just as easily as the Arduino. I can see uses for this as a sidereal clock, for example, or for various other astronomical purposes.

Also, there are many other possible display modules, with more digits, alphanumeric or graphical capability, etc. Even analog display isn't too preposterous, although I'm not going there at this stage.
 

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Well, I'll take that as interest in a productised version at some time.

One of the nice things about this architecture is that many crazy complications are really easy on the linux side, and that CPU can use the display just as easily as the Arduino. I can see uses for this as a sidereal clock, for example, or for various other astronomical purposes.

Also, there are many other possible display modules, with more digits, alphanumeric or graphical capability, etc. Even analog display isn't too preposterous, although I'm not going there at this stage.
Personally, I think you're better off with ignoring requests.

No doubt they are all very well meant, but the developer is quickly smothered by them.

Develop a car?
Sure, we'll get the wheels to support a simple frame first after that we'll think about the color of the leather.

The keep-it-simple-stupid I like a lot. Get something very simple to work first. Only then add features. One at a time.

Very simple is hard enough as it is!
 

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Personally, I think you're better off with ignoring requests.

No doubt they are all very well meant, but the developer is quickly smothered by them.

Develop a car?
Sure, we'll get the wheels to support a simple frame first after that we'll think about the color of the leather.

The keep-it-simple-stupid I like a lot. Get something very simple to work first. Only then add features. One at a time.

Very simple is hard enough as it is!
I spent most of my working life in IT so I'm well aware of how it starts with "mission creep" that rapidly becomes "feature stampede" as more and more uninformed bosses get involved. Fortunately, Andrew is answerable to nobody but himself so he's free to accept/ignore/ridicule any or all of these ideas.

To me, the idea of a TC clock is very exciting. The lack of the wristwatch constraints of size and power consumption, and the ability to program and assemble almost anything you want at low cost, opens up many opportunities. The TC+GPS (with self-calibration) or CSAC watch, that today seems almost unachievable, is clearly a practicable proposition in a clock.
 

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Discussion Starter #17
I guess I should point out that what I'm doing here is vastly overcomplicated, and mostly for my own entertainment.

If you want a premade product, this given an internet connection will be within a few milliseconds of correct. Add this to your network and it will be even more accurate and continue working without the internet connection, provided you have GPS coverage, and probably stay within a few milliseconds for a day or two without either.

And, if you want analog, here's one.
 

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Discussion Starter #18
This is really interesting, I can see the RTCs inhibition interval:

7732790
7667260
7732791
7732796
7732790
7732796
7732790
7732796
7732790
7798332
7732790
7732796
7732791
7732796
7732790
7732796
7732790
7667260
7732790
7732796
7732791
7732795
7732791
7732796
7732790
7798332
7732790
7732796
7732790
7732796
7732791
7732796
7732790
7667260
7732790
7732796
7732790
7732797
7732790
7732796
7732790
7732796
7798326
7732797
7732790
7732796
7732790
7732796
7732790
7732796

These are counts of CPU timer cycles every 1s pulse from the RTC. Note that they're mostly near 7732790 (7.7 MHz, which seems to be the current timer frequency), whereas every 16th is 7667260, which I interpret as the RTC deciding that it's a bit slow and speeding itself up.
 

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This is really interesting, I can see the RTCs inhibition interval:

7732790
7667260
7732791
7732796
7732790
7732796
7732790
7732796
7732790
7798332
7732790
7732796
7732791
7732796
7732790
7732796
7732790
7667260
7732790
7732796
7732791
7732795
7732791
7732796
7732790
7798332
7732790
7732796
7732790
7732796
7732791
7732796
7732790
7667260
7732790
7732796
7732790
7732797
7732790
7732796
7732790
7732796
7798326
7732797
7732790
7732796
7732790
7732796
7732790
7732796

These are counts of CPU timer cycles every 1s pulse from the RTC. Note that they're mostly near 7732790 (7.7 MHz, which seems to be the current timer frequency), whereas every 16th is 7667260, which I interpret as the RTC deciding that it's a bit slow and speeding itself up.
I can't remember, is NTP running on it?
NTP does a strange tweak to the frequency, but I thought that was continuously.
 

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Discussion Starter #20
No, that's the RTC's own inhibition and TC in action; the NTP process is running on the other CPU, the two aren't talking to each other regularly (yet). I have two options for how I tweak the RTC, one is adjusting the TC offset and the other the supply voltage. I haven't built hardware for voltage tweaking yet.

In other news, the interrupts are working, and so I have the display in sync with the RTC (give or take a few MS, anyway... have to measure that later).
 
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