[OpenTRV-dev] Sending Arrays via OpenTRV protocol

Jeremy Poulter jeremy at bigjungle.net
Tue May 3 20:05:50 BST 2016

I have been looking at the Tx of multiple temp values. As far as I can see
there are two options;

1) send each value with a separate JSON key. This has the advantage of
fitting in with the current architecture, will only send each value when
changed (could also be a downside depending on the use case) and will also
filter down to EmonCMS a bit easier. On the down side it will take a lot
more bytes to send a full set of temp values (and multiple frames?) and
probably need more memory from the AVR to track the values.

2) send an array of values in the JSON. Probably the more correct way of
doing it from a JSON POV and a smaller total message size, however there
are several downsides. This would be a lot more work as the simple stats
code would need changing to support values of types other than int, namely
an array of ints. There will probably be issues if the array size exceeds
the 32 bytes (IIRC) frame size, in practice limiting the size of the array
to 4 values. It could get really complicated to only send the changed
values so in effect you would need to send all the values all the time.
Let me know your thoughts.

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