Recent talk about NTP servers. It seems the limit to their accuracy is the quality of the crystal that drives the CPU clock. Most of them make really good thermometers. I'd like to try and replace the crystal on a Raspberry Pi with a signal derived from a time nut quality 10MHz standard.
The Pi uses a crystal (not a TTL can, a real two lead crystal and a pair of 47pf caps) Both leads of the crystal attach to a pair of pins on an IC. I figure I can unsolder the crystal and inject a balanced 19.5MHz signal directly to the IC's pins. I know the ARM CPU just might work on a 20MHz clock or maybe 15MHz but the video likely would not. I'm going to have to supply 19.5MHz. The question is the best way to get from 10MHz to 19.5MHz. I care only about long term (tens of seconds to days) stability. I thought of using an AD9850 DDS chip. You can buy these on break out boards very cheap on eBay but they need a 125MHz clock. I could drive the 9850 with a 120MHz clock that is multiplied up from 10MHz. what is the simplest 12x multiplier. I assume getting to 125MHz from 10MHz is to hard. New-AD9850-module-modest-capacity-AD9851-DDS-Function-Generator-up-to-40MHZ<http://www.ebay.com/itm/New-AD9850-module-modest-capacity-AD9851-DDS-Function-Generator-up-to-40MHZ-/400422353936?pt=LH_DefaultDomain_0&hash=item5d3b083c10> Is there a smarter and more direct way to get 19.5MHz for 10MHz? -- Chris Albertson Redondo Beach, California _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
