Am 15.07.19 um 22:03 schrieb Mick Sulley:
>
> latesttemp 127.688 8.875 -1.5 127.688
>
> temperature 24.9375 24.0625 23.5625 23.375
>
> So temperature is about right, but latesttemp is wildly out. I always
> thought that latesttemp was derived from temperature, temperature9,
> temperature10, temperature11, temperature12 on a DS18B20 and just from
> temperature on a DS18S20, but that is not what I am seeing here.
>
Reading
/uncached/<id>/latesttemp
reads the sampled temperature value from the scratchpad register on the
DS1820 chip while reading
/uncached/<id>/temperature
will first initiate a new temperature conversion, then read the sampled
temperature value from the scratchpad register on the DS1820 chip.
The latesttemp nodes are meant for use in conjuction with the
/simultaneous/temperature nodes. Trigger those once for all chips, read
the results from latesttemp on each chip one second later.
If you skip the /uncached part, you read from OWFS's internal cache
instead. Only if the cached value is considered as too old by OWFS, it
does the same operation as the /uncached variant.
The cache is updated in any case, but only for that single node read.
> I have always considered the DS18S20 and DS18B20 to be similar enough to
> not really prefer one over the other. Is that true or is one better in
> terms of accuracy, reliability or any other factor?
>
These are binned variants of the same chip.
The DS18S20 has 9 bit accuracy only, while the DS18B20 supports 12 bit
accuracy.
Kind regards
Jan
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