[time-nuts] PICPET- was Affordable (cheap) COTS (etc)

[Bob Stewart]

Hi Azelio,

One of the internal timers is exactly what I was thinking of.  I haven't gotten into this yet, but it looks like the dsPIC33 can accept a high quality reference clock as an input, and then use a multiplier to get it up above 100MHz.  I think 200MHz is the limit in some packages.  My idea was to run one of the timers at the internal clock rate, and use interrupts to pull out the timer values for start and stop.  Get the difference, scale appropriately, and this would be the interval plus/minus PLL jitter.  In fact, it might take a couple of timers, each scaled differently, to get a usable value from it.  I haven't looked to see the size of the timers yet.  It's just blue sky at the moment.





>________________________________
> From: Azelio Boriani <azelio.boriani at screen.it>
>To: Discussion of precise time and frequency measurement <time-nuts at febo.com> 
>Sent: Thursday, January 23, 2014 7:24 AM
>Subject: Re: [time-nuts] PICPET- was Affordable (cheap) COTS (etc)
> 
>
>It seems that that the QEI on a dsPIC are internal hardware counters
>decoding the A/B phases of optical encoders: are you sure that they
>can be used like a time interval counter? Better to use the timer
>capture dedicated input.
>
>