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Forum Index : Microcontroller and PC projects : Colour Maximite RTC update?
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5119 |
Probably been covered before. I have a Colour Maximite from Circuit Gizmo, with the built in battery backed RTC. I read somewhere, on boot, the maximite will get the current time and date info from the RTC. My question is, does TIME$ get its time from the RTC, or from the PIC's own time keeping, which was set when the chip was booted? The reason I ask is I'm building a workshop siren that will run continuously, would only be rebooted if there was a power outage, and I'm concerned about drift in time if the TIME$ isn't getting its time from the RTC. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9610 |
The 1307 RTC is drifty as hell. I'm not sure if that is what is used on the CG boards - it's been a while since I had one. You CAN replace the 1307 with a DS3232 or DS3231, and it will work. I have done this on my old CMM units a couple of times, and those RTC's are much more accurate long-term. As to the specifics of your question, my understanding is that the CMM gets the values for TIME$ and DATE$ from the RTC at power-up, but these figures are used to set the internal MMBASIC RTC, so provided you don't cycle power, the MMBASIC RTC should remain quite accurate over a period of several days or weeks. If you lose power, or cycle power daily, after a few days, you will start to see the drifty nature of the 1307's accuracy. It's a variation on the Micromite's GETTIME and SETTIME commands, except that the CMM will look for the RTC, and if it finds it, it will automatically update the PIC32's internal RTC with the values from the external RTC. I may be wrong, but that is how I understood things to work. Geoff would be the fella to confirm that or not. 
Smoke makes things work. When the smoke gets out, it stops! |
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twofingers Guru  Joined: 02/06/2014 Location: GermanyPosts: 1593 |
AFAIK yes. MAXIMITE takes his time at boottime from RTC. Anyhow, I would propose to use a DS3231 module and set the time/date per Autorun.bas. Michael causality ≠ correlation ≠ coincidence |
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TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 6283 |
Once set at powerup from the RTC, the Maximite does it's own timekeeping, just like a PC. The Maximite's crystal is as good as or better than the 1307. A few seconds a day. You could tweak the crystal but it would still vary with temperature. I would get a high precision RTC and adjust the Maximite's time daily (or more often). Jim VK7JH MMedit |
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MicroBlocks Guru Joined: 12/05/2012 Location: ThailandPosts: 2209 |
You could measure how much the maximite drifts and then adjust for it. Every day on 00:00:00 you could add/substract a few seconds. A problem with install and forget projects is that at one time it will need attention and then nobody knows how. Having a 'routine' of adjusting the time every week (or month) or so will keep them knowledgeable. If it really has to be precise and run for years then GPS enhancement could be a solution. Version X? 
Microblocks. Build with logic. |
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| robert.rozee Guru Joined: 31/12/2012 Location: New ZealandPosts: 2442 |
are there any time transmissions in australia (or new zealand) one can use for adjustment? i know that in europe there are a couple of transmissions on HF that provide tones on the hour/etc that can be used. or one could use GPS to keep the clock in check. something that generates NMEA strings out of a serial port. or a nearby PC that can send the odd timestamp string to the maximite. cheers, rob :-) |
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Justplayin Guru Joined: 31/01/2014 Location: United StatesPosts: 328 |
I use this method on my DVR PC. The DVR needs to maintain fairly accurate time, but the PC is not connected to the internet. So, every hour I reset the PC time using GPS data. Windows even handles the UTC to Local time conversion when you use the proper API call to set the system time. 
--Curtis I am not a Mad Scientist... It makes me happy inventing new ways to take over the world!! |
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| robert.rozee Guru Joined: 31/12/2012 Location: New ZealandPosts: 2442 |
the ceapest GPS modules (with onboard antenna) on ebay seem to be these ones: http://www.ebay.com/itm/281505145902 VK16E module, 9600 baud serial output, just under us$10. like many of the different modules available from china on ebay, over time there seems to be a fair turnover - what is available this week is no longer sold a year later. the EM408 that geoff used in a micromite clock design a year back seems to be all but vanished. cheers, rob :-) |
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OA47 Guru Joined: 11/04/2012 Location: AustraliaPosts: 986 |
Rob this may make it difficult for Glenn Shipping: Does not ship to Australia | See details Item location: shenzhen, China Ships to: Worldwide See exclusions |
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| WhiteWizzard Guru Joined: 05/04/2013 Location: United KingdomPosts: 2944 |
Hi Rob, There's an opportunity for you to order some in for us folks in Australia and UK (and Hawaii!)
WW |
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| robert.rozee Guru Joined: 31/12/2012 Location: New ZealandPosts: 2442 |
this one ships to australia, for just a few cents more: http://www.ebay.com/itm/171556498506 and this one to the UK: http://www.ebay.com/itm/181594912168 cheers, rob :-) |
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palcal Guru Joined: 12/10/2011 Location: AustraliaPosts: 1993 |
I have used the V.KEL VK16E and it works well. Paul "It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all" |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5119 |
Thanks guys. I'll do some tests to see how much drift I have. The RTC seams to be spot on so far, to the minute at least. I set the time a couple of weeks ago and its still good. But I'll order a GPS module anyway. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| VK2MCT Senior Member  Joined: 30/03/2012 Location: AustraliaPosts: 120 |
Does anyone know (especially Paul) whether a V.KEL VK16E GPS rx is likely to work under an Aussie Tile roof? Or near a window ? Thanks John B |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5119 |
I would imagine tiles wont have much effect on GPS signals. A steel roof however can be a problem, it depends on how close you are to a non-steel wall or window. OK, early tests so not very accurate. The PIC looses about 0.5 seconds a day, the RTC looses about 1 second a day. Question is, will the following reset the RTC to the PIC's time? TIME$=TIME$ ? I assume when you do a TIME$= it will update the RTC as well as the PIC. So once a week I could add a few seconds to the PIC's time, then issue a TIME$=TIME$ to update the RTC? Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 6283 |
I think you need RTC SETTIME and RTC GETTIME. I don't have a CMM with RTC to test. Jim VK7JH MMedit |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5119 |
I've added the following code to help keep better time. The user can set a fine adjustment in the menu, basically how many milliseconds to adjust the clock every midnight. At 15 seconds past midnight, the following code is run... if TimeOffset<0 then Pause 0-TimeOffset Time$="00:00:15" endif if TimeOffset>0 then Pause 1000-TimeOffset Time$="00:00:16" endif Pause 1000 where TimeOffset is the preset millisecond adjustment. The code is fired at 00:00:15, pauses for a few milliseconds ( TimeOffset ), then resets the clock either back or forward a second, depending if its a negative offset or not. Its triggered at 15 seconds past midnight because at exactly midnight there is a siren event in the code for night shift lunch break. The final Pause 1000 delay is there to stop the code running more than once. My main code loops every 100 milliseconds, so events like this can be re-triggered if no delay is added. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| palcal Guru Joined: 12/10/2011 Location: AustraliaPosts: 1993 |
@ VK2MCT Sorry I'm late I wasn't following the thread. I find that receiving the time only is always OK, I have a GPS clock that seems to work anywhere. But when I use the lat. and lon. coordinates it is a different matter, not very reliable indoors. I can't explain why the time is easier to receive except that maybe you only need one satellite for time and many more for accurate location. I have been working with EM408 and V.KEL modules for about 3 years and haven't found any difference. In my workshop with metal roof I use an antenna I bought from DealXtreme for about $5. Paul. "It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all" |
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