[time-nuts] IRIG B

Bob Camp lists at rtty.us
Tue May 25 21:14:59 UTC 2010


A lot of the codec's talk I2S. That's not a real popular item in the
embedded processor world. If you are already running a FPGA, the IRIG might
fit in the "empty" part of the chip. You often have to bump up 1.5 or 2:1
when you run out of this or that. 


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Hal Murray
Sent: Tuesday, May 25, 2010 2:50 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] IRIG B

> The IRIG-B decoder work I did was implemented on power systems relays &
> disturbance recorders several years ago, then I left the company and in
> meantime, they changed over to an FPGA implementation and skipped the
> processor altogether.  Now I'm back with that same company (although
> ownership has changed), but I haven't yet had a chat with the new FPGA
> designer to find out how he did it :-)

Interesting.  I'd like to know why they switched to FPGA.

I thought the consensus in the FPGA world was that if you could do it in 
software that was probably the better way to go.  The main idea is that it's

easier to hire programmers than FPGA designers.

I'd expect silicon costs to be roughly equal.  In a FPGA you are "wasting" a

lot of silicon for routing.  In a CPU, you are wasting it on instruction 
decoding.  Both are high volume parts riding the crest of Moore's Law.  Of 
course, algorithm details may push you one way or the other.

> I've also tweaked and "upgraded" (well in my opinion) the TG program of
> NTP package, which generates WWV(H) and IRIG-B audio signals in *NIX
> operating systems.  It was targeted for the Sun Sparc and I moved it to
> audio which was what I was using on X86 GNU/LINUX at the time.  I think I
> submitted it for inclusion in the NTP package but I don't think it ever
> in there; I used to claim that it was rejected, but then again it's also
> possible that I didn't submit it correctly.  I can give this to you if you
> would like. 

It's in there.  Thanks.  I called it tg2 because I couldn't test it in the 
Sun world and I wanted to make sure I didn't break anything.

The recipe for getting fixes into the NTP package is pretty simple: find an 
insider who likes your changes.  Mechanically, their bugzilla is at 
That tracks enhancements/wishes as well as bugs.  You can upload diffs and 

These are my opinions, not necessarily my employer's.  I hate spam.

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