[Coco] Clock chips

Fri Dec 20 22:35:26 EST 2013

Mark,

That's well and good for a system that tied to the internet.  But most 
CoCos are stand alone devices without a network connection.

The message was directed to the CoCo community in general with a 
solution to older RTC devices based on DS 1307.  That's why I did not 
start message with "Mark,".  Next time I see your name in the message I 
will start the message "Not to Mark but the CoCo Community," if not 
directed just to you.

Sorry for the confusion.

As for the DS1307 drifting a little, the DS1307 does not drift. It's the 
Crystal that drifted and should be replace a better Crystal.  I've 
replaced 32.768kHz Crystals that have dropped to just 29.5 KHz.  In my 
book, that's a big drift!

Steve

On 12/20/2013 5:00 PM, Mark Marlette wrote:
> 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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