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Forum Index : Microcontroller and PC projects : cgcolormax2 very bad time accuracy

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MicroBlocks

Guru

Joined: 12/05/2012
Location: Thailand
Posts: 2209
Posted: 11:24pm 18 Oct 2013
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The reason i want to try is that when the CMM is used as an embedded controller it might not restart for weeks, even months.
If the RTC is read only at startup the time will drift a lot over long time spans.
Mine drifts about 10 seconds each day. I have a CMM based on a UBW32.
My thinking was that synchronizing the system time with the RTC time every day would eradicate that problem.

I have a particular need for two i2c busses so that i can set one in slave and the other in master. That has to be changed in the firmware and i will need to study that. Which will be a good way to learn more about it. So i am not complaining. :)

Microblocks. Build with logic.
 
Lorenzo

Newbie

Joined: 27/08/2013
Location: France
Posts: 17
Posted: 04:20am 20 Oct 2013
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Geof,

Effectively,

I just read the code:

340 TIME$ = "0:0:0" ' Zero the clock it's explicit.

This is an interesting little demonstration program, I think you already think in an update, perhaps also improvements for the next revision of the MMbasic library...


Lorenzo.

Edited by Lorenzo 2013-10-21
 
Grogster

Admin Group

Joined: 31/12/2012
Location: New Zealand
Posts: 9308
Posted: 11:28pm 22 Oct 2013
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If you want REAL accuracy, then use the DS3232.

This IC is a very VERY accurate RTC, and the crystal reference is internal to the chip.

However, the 3232 is about four times the price of the 1307, but I have had issues with the 1307 before today, in terms of it's drifting time - over time. ;)

Having said that, it is easy enough to design a routine into your code, so that you can update the time once you notice it is out by a bit - not really that painful to do, and having said all the above, I am happy enough to stick with the 1307, and just alter the clock in the menus as and when needed, which is not really that often.
Smoke makes things work. When the smoke gets out, it stops!
 
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