On Thu, Aug 20, 2009 at 9:06 AM, Tony Smith wrote: > All the units I've got (various brands, all cheap ones) keep very good ti= me. > I tend to carry one in my pocket instead of wearing a watch, a nerdy fob > watch if you will. > > I'm guessing they've got the ubiquitous 32k watch crystal in them, I've > never opened one up to see. =A0More than enough to keep up with a 13Hz si= gnal. > If you want a 1 second source the pulse generator out of a cheap clock wi= ll > do (they use a 32k crystal too). > > The OP should do the display in binary or something. =A0Maybe PWM a panel > meter. There is no need for that. I already have some RTC chips that take care of everything through an easy to use I2C interface. All they need is a backup battery which lasts for years and keep time VERY accurately. Also generate a 1s pulse if required. I read through more of the family datasheet of the dsPIC33 (especially on the CCP module). Turns out that I can use the CCP module in capture mode for period measurement (which is just what I need) and hook up an appropriate crystal to one of the 16 bit timers. I guess I'll use a reed switch. -- = http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist