Regarding timestamps Paul Alfille mentions that "..the timestamp for the
reading is kept in the cache hash table and isn't exposed to the rest of
the program."
I would like to either create a new owfs property (file) for timestamp
or modify the timestamp mtime of each file that is updated. For
example, when a temperature sensor is converted, a new file
/ID/timestamp is created and contains the current unixtime (it will also
have a ctime == the current unixtime).
Is this a horror show to do?
Why do this? For cached values it will be instructive to know the time
the value was read. This is because certain calculations are
time-critical. Even 15 seconds can make a difference when comparing
temperatures between two points for, say, a differential temperature.
So if I read a cached value timestamp for two values I wish to evaluate
and find they are more than 10 seconds apart, my program will wish to
read each one manually (/uncached) to get the reading time as close as
possible. It is inefficient to do a manual reading every time for these
sensors. The same is true for reading a counter where the counter is
(another example) attached to a flow sensor. If I do not know the time
the counter reading was done, yet assume it's "now", the value I report
for "now" may be quite different if the reading was taken 30 seconds ago.
Does someone have a template or description of how things are glued
together, so when I add this functionality I hit all the bases?
Or other suggestion?
--
On the subject of my example where two temperature sensors need to be
read, let's say these are on the same one wire segment. It would be
sweet, in cases where I have to manually read these sensors, if there's
a command or other technique that causes a 1-wire global conversion to
be issued for all temperature sensors on the given segment. This way we
hit both at the same time.
Perhaps this is already done - when I read one sensor manually, all
temperature sensors on the same segment convert, too? This would be
sweet if so.
/m
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