Kasper, I like your style! Small ROM = no inessential features! I shall be studying this code, getting capture working with no capture hardware is a real pain.
On 2 January 2012 00:53, Kasper Pedersen <time-n...@kasperkp.dk> wrote: > On 01/01/2012 12:23 PM, Tom Harris wrote: > >> I too have been mulling over a minimal GPSDO. >> >> Has anyone mentioned a PWM DAC? Even a "toy" microcontroller like the >> Atmel AVRs can generate 16 bit resolution PWM, which sounds like it > > .. > >> So a minimal GPSDO looks like a simple microcontroller (I would use >> Arduino since we use these at work whenever we need to build something >> in an afternoon) with a filter for a PWM DAC, so one opamp and a few >> discretes. Of course as I write software for such beasts as a trade I >> am giving the software a zero cost. >> > > > A 'bike light' sized microcontroller can do the job. Today I would have > used something larger, and saved development time. On the other hand, > having only room for 512 instructions prevented spending time on > non-essential features. > > http://n1.taur.dk/simplexdo/ > > I used 8 bit PWM into a two-stage RC filter, making it easier to filter. > To get 16 bit resolution I added delta-sigma modulation on top of the PWM. > > The ATTiny13 is not the right part for the job; It has no input capture. > So space- and time consuming tricks are necessary to get cycle-accurate > capture. > > Recently I discovered that some of the microcontrollers in the drawer > would do nanosecond capture all on their own, but with a working tbolt, > need has been lacking. > > > /Kasper Pedersen > > _______________________________________________ > 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. -- Tom Harris <celephi...@gmail.com> _______________________________________________ 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.