[OpenTRV-dev] I just added this to the data sets doc...

[Damon Hart-Davis]

The leaf nodes are not expected to maintain or transmit accurate time: the concentrator node adds timestamps.  See here, item 3 in the Decisions section:

http://www.earth.org.uk/OpenTRV-protocol-discussions-201411-1.html

Rgds

Damon


> On 23 Jun 2015, at 09:24, Bo Herrmannsen <bo.herrmannsen at gmail.com> wrote:
> 
> btw... and not related to JSON... but could a time stamp of some sorts be put in so that one unit can be the master clock for the others?
> 
> Since my unit at the hotwater cylinder is mains powered and the rest on battery it would be nice to just replace battery and they listen for the time from the DHW unit... 
> 
> just a quick thought 
> 
> 2015-06-23 10:12 GMT+02:00 Damon Hart-Davis <dhd at exnet.com>:
> Hi Y’All,
> 
> Bruno and I were having a discussion yesterday afternoon about how properly to represent for *JSON* transmission values with units that can be automatically translated to SenML/UCUM units, that are easy for an MCU to generate (eg no floating point if possible), that remain human readable and reasonably compact, and that deal with values whose natural representation is with some power-of-2 multiplier to capture all the significant (binary) digits with minimal bloat in the decimal int expansion.
> 
> http://www.earth.org.uk/note-on-IoT-data-sets-and-processing.html#binshiftrep
> 
> Any thoughts?
> 
> Rgds
> 
> Damon
> 
> 
> 2015/06/22:
> Bruno and Damon discussed the desirability of completely mechanical conversions
> from JSON sensor units to UCUM/SenML units to minimise or eliminate magic
> 'mappings' that require sophisticated developer time (in line with IBM
> suggestions).  One particular issue that cam eup is being able to represent
> value as integers (for brevity and to keep code small on the sensors)
> and scale to integers for transit, when the natural scaling is a power of two,
> eg temperatures from common sensors with four significant bits after the binary
> point, ie that are currently being sent with units <code>|C16</code> for
> "Celsius times 16".  Bruno was going to investigate.  One possible escape
> hatch is with the Ki/Mi/Gi/Ti "special prefix symbols for powers of 2".
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