On 06/02/2013 10:21 PM, Attila Kinali wrote: > > Another stupid idea: You have a 19.5MHz crystal, probably some > odd PLL and a varicap diode lying around: Build a VCXO out of the > crystal and lock it to the 10MHz using the PLL. >
It has been done with an xor gate, a couple of passives, and the varicap diode. There processor performs as the divider: This bit of code will configure the gpclk0 block to output 10MHz on pin 7 of the connector: http://n1.taur.dk/pi10MHz.tgz The signal on the pin is the 19.2MHz crystal multiplied to 500MHz (the GPU PLL), and then divided back down to 10MHz. Feed that signal, and the external reference signal into an xor gate or other phase detector of choice. Put an RC filter of around 50us on the output, and connect that to the varicap. Picture of the thing as built: http://n1.taur.dk/piclock.jpg The only thing on the other side of the board is the connector and the 74HC86 in DIP. I don't know what my varicap is, it came out of an old gps receiver. /Kasper Pedersen _______________________________________________ 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.
