This one is software adjustable in case it runs slightly fast or slow.
K8LH Novelty Single Chip Clock
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25th August 2008 12:17 PM #113v0
Coop Build CoordinatorThanks mike. I was not actualy building this clock
But it looked like a good context for asking the question.
0Please post questions to the forums. PM's are for personal communication.
BCHS/3v0's PIC C18 Tutorials
Mondo Tech's Super Probe
Brian Schmalz's USB Bit Whacker
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9th September 2008 04:40 AM #12Space Varmint
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9th September 2008 02:41 PM #13Pommie
What a horrible piece of code and it uses Timer0. If you do a search Mike (the OP) posted a very good method to adjust for crystal inaccuracies in software.
Originally Posted by Space Varmint
Mike.0
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9th September 2008 02:49 PM #14blueroomelectronics
Personally I'm one of those types who tries to match the crystal frequency to the task at hand. Using the generic 4MHz or multiples thereof for everything always baffled me, after all crystals are about the same price and there are many common frequencies available. 19.6608MHz is a handy for both RTC & UART stuff.
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10th September 2008 01:37 AM #15wy6k
Just use current limiting resistors on the segment lines and connect the transistor collectors to 12 volts and you can have whatever brightness you want.
If you want to keep it a one power supply project, use 12 volts as the power supply and generate the 5v with a voltage regulator (7805).
Mike0
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10th September 2008 07:07 AM Thread Starter #16Mike, K8LH
Hi Mike, WY6K, Originally Posted by wy6k
Keeping in mind the 5v PIC pins, an NPN/PNP pair or N-FET/P-FET pair for the high side drivers does indeed work well with traditional multiplexed displays but it's a bit problematic for Charlieplexed displays.
Regards, Mike, K8LH0
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10th September 2008 07:18 AM Thread Starter #17Mike, K8LH
Unfortunately, that's about all that crystal frequency is good for (grin). Originally Posted by blueroomelectronics
Using wierd crystal frequencies always baffled me but if you can show me how to accomplish any operation in exact 1 usec increments using one of those crystal frequencies then you'll have a convert (grin)...0
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10th September 2008 07:58 AM #18Pommie
I can see how a 19.6608MHz crystal is good for serial communications but how is it any better for a real time clock?
Mike.0Last edited by Pommie; 10th September 2008 at 07:58 AM.
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10th September 2008 08:30 AM #19Nigel Goodwin
Super ModeratorI can't see how it's any better for serial either, it works 100% perfectly with a 20MHz or 4MHz crystal - so how does getting an exact frequency match give any improvement?. Originally Posted by Pommie
I can see how a 19.6608MHz crystal is good for serial communications but how is it any better for a real time clock?0PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk
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11th September 2008 12:26 AM #20wy6k
Ahhh. I see that now. In that case, you need another set of column transistors and invert the logic on the n-1 line? (I'm not really familiar with Charlieplexing, but I think I get it). MPU output drives base of NPN which pulls down the base of the PNP with it's emitter connected to 12 volts. Right? Originally Posted by Mike, K8LH
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