|Re: WP34S - possible to correct RTC in SW?|
Message #4 Posted by BobVA on 12 July 2011, 11:41 p.m.,
in response to message #3 by Paul Dale
The lowest crystal spec I've seen for 32 KHz crystals is around 20 ppm and I'm seeing significantly greater errors. I suspect it's more likely the caps aren't exactly the correct values consequently pulling the frequency off.
I was tinkering with exactly the program you suggested as a fix when I discovered the lack of auto execute. But running it manually as you suggest may make more sense now that I think about it - why fix it until you need it?
Actually that suggests another approach. Could the correction routine be added to the "TIME" function (i.e. the correction gets run when TIME is called)? I was thinking of writing a user program replacement for TIME to do this, but perhaps it's worth including in the firmware?
I see two ways to do it - either reset the clock with the corrected time on every call, or just compute and store a bias value in EEPROM, and add it to the RTC value when TIME is called (saving the time/effort of actually resetting the clock).
Re: Autorun flag. Well, you can't play all those fabulous tricks on your friends that we used to do back in the 41c/42c days using it :-)
Allen: Well, it IS running fast. If my math is correct all I need to do is to store in a drawer that's moving at 3.5E6 m/s and that would fix it right up....
Edited: 13 July 2011, 12:01 a.m. after one or more responses were posted