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.
John
----
On 11/24/2016 02:49 AM, Andrew Rodland wrote:
On Wed, Nov 23, 2016 at 10:48 AM, John Ackermann N8UR <j...@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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