[time-nuts] New Timestamping / Time Interval Counter: the TICC

John Ackermann N8UR jra at febo.com
Sun Nov 27 10:04:59 EST 2016

Good guess.  The 10 MHz reference drives all the logic on the board, and 
particularly the counter that maintains a local timescale in 100us 
increments; the TDC7200 interpolates between the 100us ticks to stamp 
incoming events on channel A and/or B with picosecond precision.  The 
stamps on both channels are referenced to the same local timescale.

Therefore, you can do a measurement of a PPS source against the 10 MHz 
reference and the resulting timestamp output can be processed by TimeLab 
or whatever into stability data (the requirement being that the software 
knows how to deal with timestamps that increment by the nominal 
measurement rate, e.g., 1 second per measurement for PPS data).

So with PPS from GPSDO "A" on channel A the timestamp output after 
unwrapping will show the phase of A vs. 10 MHz.

You can add PPS from GPSDO "B" on channel B and the TICC will also 
output timestamps of B vs. the 10 MHz source.

If you want, you can subtract A from B to get the time interval between 
the two GPSDO, since both timestamp measurements are against a common 
timescale.  The TICC has a mode to output the (B-A) difference, so it 
can act as either a traditional time interval counter, or as a 
two-channel timestamping counter.

And as noted in my other message to Luciano, the TICC can also output 
both timestamp and time interval data simultaneously to allow 
three-corner-hat measurements of (A-C, B-C, B-A) where C is the 10 MHz 


On 11/27/2016 09:24 AM, Bob Camp wrote:
> Hi
> Without doing a bunch of actual *work* I’m not sure what is inside the guts of the board. Being
> lazy I’ll just guess ….
> There appears to be a 10 MHz time base input and a pair of measurement inputs. In a lot us will
> be comparing to a “house standard”. That standard has a pps output that is related directly to
> the 10 MHz reference. If I can uniquely identify one edge (out of 10 million edges) as the right
> edge, I can use the 10 MHz as my pps reference. Put another way, I don’t really need to measure
> a pps input from the house standard if I’m already locked up in phase to the 10 MHz. All I need to
> do is to tag an edge / reset a counter.
> The advantage of this is that I may not need another fancy TDC chip to set up the reference. I can
> use *both* inputs for DUT’s rather than using one as a reference.
> Part of the reason I’m guessing this would work is the claim that boards can be stacked for multiple
> input setups ….
> Bob
>> On Nov 27, 2016, at 7:36 AM, timeok <timeok at timeok.it> wrote:
>>    Hi John,
>> I have planned to buy two TICC.
>> An interesting feature would be to be able to do two simultaneous acquisitions,
>> and Timelab as real time display,using the two indipendent input channels and the 10Mhz clock as single reference.
>> Luciano
>> www.timeok.it
>>    From "time-nuts" time-nuts-bounces at febo.com
>>    To "Discussion of precise time and frequency measurement" time-nuts at febo.com
>>    Cc
>>    Date Wed, 23 Nov 2016 10:48:57 -0500
>>    Subject [time-nuts] New Timestamping / Time Interval Counter: the TICC
>>    Counters with resolution below 1 nanosecond are difficult. They require
>>    either outrageous clock speeds, or interpolators that are typically a
>>    bunch of analog components mixed with black magic and stirred by
>>    frequent calibration. The very best single-shot resolution that's been
>>    commercially available is 22 picoseconds in the HP 5370A/B, with jitter
>>    somewhat more than that. My 5370B has an one-second noise ADEV of about
>>    4x10e-11.
>>    With the help of some very talented friends, I've been working on a new
>>    counter called the "TICC" with <60ps resolution and similar jitter,
>>    based the Texas Instruments TDC7200 time-to-data-converter chip. The
>>    noise ADEV is about 7x10e-11, not much worse than the 5370,
>>    but here's the trick: the TICC is an Arduino shield (mounting a Mega
>>    2560 controller) that weighs a couple of ounces, requires *no*
>>    calibration, and is powered from a USB cable!
>>    The TICC is implemented as a two-channel timestamping counter. That
>>    means it can measure or two low-frequency (e.g., pulse-per-second)
>>    inputs against an external 10 MHz reference, or it can do a traditional
>>    time interval measurement of input against the other. It can also
>>    measure period, ratio, or any other function of two-channel timestamp
>>    data. (And by the way -- multiple TICCs can be connected to yield 4, 6,
>>    8, or more synchronized channels, though we haven't tested this
>>    capability yet.)
>>    I've attached a picture of the TICC prototype as well as an ADEV plot of
>>    a 17+ day run of multiple measurements taken by two TICCs, and also
>>    showing the TICC noise floor. The good news behind that plot is that
>>    there are more than 6 million data points behind these results, and
>>    there was not a single glitch or significant outlier among them.
>>    There's more information available at http://febo.com/pages/TICC
>>    The software is open source (BSD license) and is available at
>>    https://github.com/TAPR/TICC -- the current version seems be reliable
>>    but there are still features to add and a *lot* of cleanup to do; it's
>>    currently ugly and very much a work in process.
>>    As always, I'll be making the TICC available through TAPR. We're still
>>    finalizing details, but we expect the price to be less than $200 for a
>>    turn-key system: TICC mounted an Arduino with software loaded and
>>    tested for basic functionality. We hope to ship the TICC by February.
>>    I'll post a note in a week or two with final price and ordering
>>    information. As a heads up, we will probably offer a small discount for
>>    pre-orders. TAPR is a shoestring non-profit group and the up-front cost
>>    to manufacture this unit will frankly be a challenge for us. Getting
>>    pre-orders will help our cash flow significantly, so we ask you to keep
>>    that in mind.
>>    John
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