[Coco] Clock chips

[Mark Marlette]

Steve,

Yes....as you can see my statement was to remove the DS1307 and use a software RTC.

The DS1307 drifts little... The software RTC is derived from the system clock, 16/32MHZ depending on which dev platform I am on. On the Xmega I can hook a 32.768kHz xtal to have a precision clock source as it has DFLL.

Yes my firmware allows in the .cfg file on the SD to set the user's offset from UTC and does DST and adjusts as required.

All on the CoCo.....well kind of.... :)

I don't need to check the time, as I know it is always correct, at least within a second.

Regards,

Mark
http://www.cloud9tech.com




________________________________
 From: Steve <6809er at srbsoftware.com>
To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com> 
Sent: Friday, December 20, 2013 6:30 PM
Subject: Re: [Coco] Clock chips
 

The loosing of time with DS1307 is never do to the DS1307 chip itself, 
but the Crystal connected to it.  A new crystal with more accuracy will 
home it to only off by a second or two a day.

In one project, the DS1307 was off by a bit under 1 second a day. So, I 
added code that on Sunday at midnight would added 6 seconds.  This 
standard alone computer is only off by 1 second a month.  This is 
important since this computer is the Church's Bell Tower system and the 
chimes must be on time.

While I do check the time on the computer a few times a months, I don't 
need to adjusted it more than once or twice a year.

The program also adjust for U.S. Daylight saving time so I don't have to 
show up on those Sundays when the U.S. time shifts.

By the way, Crystal can lose their accuracy of time.  If they're older 
than a decade, it maybe time to replace them.  With yours loosing 120 
seconds in 24 hours, it times to replace the crystal.

The PDF states this about the Crystal...

/Connections for Standard 32.768kHz Quartz Crystal. The internal 
oscillator circuitry is designed for operation with a crystal having a 
specified load capacitance (CL) of 12.5pF./

Jameco price for a new Crystal is only $0.49 with the Frequency 
Tolerance at +/- 50 PPM or about 0.00254% off.  But even with that 
accuracy, it will off by up to 2 seconds a day.  The problem is the min. 
shipping cost.  It's high at $4.00 to $7.00 in the U.S.

the 
link:http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_325244_-1

Over at taydaelectronics.com they have it for just $.011 with a 
Frequency Tolerance at +/- 20 PPM or about 0.0001% off or less than a 
seconds a day.  While they are in THAILAND, the prices are low and the 
shipping is not too bad. This part (1 or 10 of them) only had $1.00 for 
standard rate U.S. shipping.  It may take week to 10 days for the lowest 
price shipping, but they are cheaper than any U.S. parts house I've found.

The Link: 
http://www.taydaelectronics.com/32-768-khz-crystal-cylender-3-x-8-mm.html

I've been selling a number of "kits" and found taydaelectronics.com a 
good source for small electronic parts. Not one problem in the eight 
months that I've been using them.

Steve



On 12/20/2013 12:19 PM, Mark Marlette wrote:
> Brian,
>
> Currently my projects have a DS1307 in them.
>
> **Might** remove  and go with a software RTC, it looses time at about 1min per 12hrs. That is terrible of course.
>
> I do have SNTP client taking care of that issue though.... yep on a CoCo. :)
>
> You can have four different time servers in a config file on the SD, refresh and retry intervals definable as well.
>
> The DS1307 is cheap enough that I'll probable leave it in, in case an Internet connection is not available for a good period of time.
>
> Also have SMTP, NO-IP Update client and Web Server as well all in 24K of code. :)
>
>
> Been spending my time on the development of this firmware...need to get back to the other projects......
>
> Regards,
>
> Mark
> http://www.cloud9tech.com
>
>
>
> ________________________________
>   From: Brian Goers <briang0671 at sbcglobal.net>
> To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
> Sent: Friday, December 20, 2013 1:50 PM
> Subject: [Coco] Clock chips
>  
>
> If I was to thinking out loud?
> What clocks chip could we putin our system?
> Not cause errors in our systemsand not be difficult to install.
> Can it be placed in any Color Computer 1, 2 or 3?
>


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