---------- Forwarded message ---------- From: Don Latham <d...@montana.com> Date: Fri, Sep 14, 2012 at 2:01 PM Subject: Re: [time-nuts] GPSDO control loops and correcting quantization error To: Discussion of precise time and frequency measurement <time-nuts@febo.com>
Michael: Actually implementing a 16 bit DAC to its 1-bit minimum resolution will be headache enough. You will gain a real education in good grounding practice, shielding, power supply stability and noise, and other Murphy intrusion. A 32 bit DAC IMHO, is impossible, and that's the name of that tune. I think the step size would be close to the same with the 32 bit DAC but the reason you use it is so you can control just about any OCXO, Rb or other things you drop in. In other words I'd use the extra bits to extend the voltage range. But while in use, I doubt you'd ever change the highest 16 or 18 bits Also if you are building a general purpose controller for OCXOs and Rb, remember that some Rb oscillators use RS-232 control to set the frequqecy. It might be good to build in an RS232 port. The firmware in the uP can always be changed but hard to add the DB9 connector later. One otherthing I was doing when I was working on a design like this was to discipline both an XO and an Rb from the same GPS. Almost like building two controllers but you save some because you can use one uP and one GPS interface. Now that you have a disciplined Rb it can be used for hold over in case the GPS goes away. I thought it would be unlikely for GPS to actually fail but allowing for hold over would make the entire unit portable. Chris Albertson Redondo Beach, California _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.