On 26 Mar, 2012, at 12:56 , Chris Albertson wrote:
> On Mon, Mar 26, 2012 at 12:50 PM, Attila Kinali <att...@kinali.ch> wrote:
>> Moin,
>>
>> I have the numbers together for the group buy of the u-Blox LEA-6T.
>
> I have not been able to locate a spec sheet for there. Do you have a
> link? Or maybe you could say how these are improved over the M12M?
Apart from other issues it may potentially provide significantly
more accurate time for computer timekeeping via the Time Mark input,
depending on the accuracy of measurements on that input.
That is, rather than connecting the PPS output to a computer input pin
and then trying to timestamp when the interrupts occur, one can instead
tie an output pin from the computer to the Time Mark input and poll
for timestamps measured by the LEA-6T, say with a programmed sequence like
<get computer clock timestamp>
<toggle Time Mark pin>
<get computer clock timestamp>
. . .
<ask LEA-6T for Time Mark timestamp>
If done well that may get the time ambiguity at the computer end down from
the > microsecond level of interrupt latency to the < 100 nanoseconds it
should take for a PIO write to a hardware register to complete. If the
LEA-6T takes Time Mark timestamps with that precision then this may be a
significant improvement.
Dennis Ferguson
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