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

Anders Wallin anders.e.e.wallin at gmail.com
Thu Jan 23 06:31:40 EST 2014


Given that Arduinos are now sold in (almost) every super-market, and the
programming IDE is free/open-source, and the C/C++ code is familiar to
many, I would have thought the logical evolution of the "pictic" is to
become an Arduino shield?

One drawback (AFAIK) is that e.g. Arduino Due doesn't have a dedicated
counter/encoder input, like the dsPICs made for motor-control have.
On the other hand the Due has 12-bit analog inputs (and DACs) that might
work for interpolation.

How fast can the QEI (quadrature encoder interface) on a dsPIC clocked at
140MHz count? Were you planning on using a dsPIC with two QEIs, for TIC
start&stop coarse counting?
For 1ns or 2ns resolution an analog (or fpga?) interpolator is required
anyway?

AW


On Thu, Jan 23, 2014 at 4:10 AM, Tom Van Baak (lab) <tvb at leapsecond.com>wrote:

> Hi Bob,
>
> It's pretty easy to get a tiny PIC or AVR down to 50 ns, so to me the next
> sweet spot would be 1 or 2 ns. A couple of us are trying. Contact me
> off-list re the dsPIC33.
>
> /tvb (i5s)
>
> > On Jan 22, 2014, at 5:53 PM, Bob Stewart <bob at evoria.net> wrote:
> >
> > Tom,
> >
> > Do you know of any other PIC projects that get a greater resolution?  I
> was thinking of doing something with a dsPIC33 running at 140MHz or
> greater, but I'm not sure I want to devote the time to if it's it's been
> done.
> >
> > Bob
> >
> >
> >
> >
> >> ________________________________
> >> From: Tom Van Baak (lab) <tvb at leapsecond.com>
> >> To: Robert Atkinson <robert8rpi at yahoo.co.uk>; Discussion of precise
> time and frequency measurement <time-nuts at febo.com>
> >> Sent: Wednesday, January 22, 2014 7:39 PM
> >> Subject: Re: [time-nuts] Affordable (cheap) COTS / eBay kit for TIE /
> 1PPS phase comparison
> >>
> >>
> >> As much as I'm fond of my picPET it has 400 ns resolution and not
> intended to replace a 5 or 10 or 50 ns TIC (which is what the OP asked for).
> >>
> >> /tvb (i5s)
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