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

John Ackermann N8UR jra at febo.com
Thu Nov 24 09:50:10 EST 2016

Thanks, Andrew.  Yes, it is weird how the Arduino folks choose what 
capabilities to expose on the board.  From some testing I did, it seems 
that the Arduino handles the 100 kHz interrupt rate without too much 
strain -- it became a bigger issue at 250 kHz or above -- but the timers 
would have been a more elegant approach if they had been available.


On 11/24/2016 02:49 AM, Andrew Rodland wrote:
> On Wed, Nov 23, 2016 at 10:48 AM, John Ackermann N8UR <jra at febo.com> wrote:
>> The TICC is implemented as a two-channel timestamping counter.  That means
>> it can measure one 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 one 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.)
> Very exciting, I will definitely be wanting one :)
> There's *almost* a way to do the coarse timer counting with almost no
> CPU overhead, but unfortunately the Arduino folks were terribly
> inconsistent about which timer signals they decided to assign to
> Arduino pins. Of the six external clocks for timers, they brought out
> two (T0 and T5), and of the four input captures, they brought out two
> (ICP4 and ICP5). If they had brought out T4 then with a little bit of
> timer configuration you could use COARSE to clock TIMER4 and TIMER5 in
> lockstep, run STOP_A and STOP_B to ICP4 and ICP5, and instead of
> interrupting at 10kHz to increment PICcount, you would only have to
> interrupt every 6.5536 seconds to increment the upper bits. Plus
> handling the actual events of course. I find that very appealing, but
> unfortunately, T4 is out of reach of a shield.
> Andrew
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