On 21 lis 2013, at 23:47, Adam Jacobs <[email protected]> wrote:
> I used to think it was strange too and always included the clock > functionality in the microcontroller. However, I was always fine-tuning the > accuracy. I believe that someone was posting to this list a little while back > about his own Atmel microcontroller clock-code accuracy issues. I had clock accuracy issues with my MSP430-based clock until I remembered to properly set the load capacitance for the 32.768kHz crystal. After changing it to 12pF the clock runs incredibly well. As for battery backup, the chip detects external power failing and quickly switches into a power-saving mode, where it does pretty much nothing except wake up every second to increase the counter (I use the watchdog timer for that). It also checks the voltage. In this mode, the power consumption is down to single microamps, so a single CR2032 can last for years. It worked better than I expected it to. I was never fond of external RTC chips because of their prices. I try to design cheaply, I think this approach forces you to design better. And I try to never design in a part that is not available (samples don't cut it). I'll use it only if Farnell or RS stock it. This rules out most Maxim parts, unfortunately, because while often the best fit, they are usually unobtainium. Exceptions can be made for chips like 74141 or the MAX6921, which can be gotten from eBay. Going back to the RTC, I think implementing the loops that count seconds, minutes and hours is a really fun experience, the "going to the basics" kind you very rarely get. --J. -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send an email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/E5579BE3-89A4-4E86-9C6D-56AC30DEF42D%40gmail.com. For more options, visit https://groups.google.com/groups/opt_out.
