[OpenTRV-dev] V0.2-Arduino: getting started

[Damon Hart-Davis]

Hi,

On 1 Apr 2013, at 14:46, Mike Stirling wrote:

> One thing not being considered here is value to OEMs.  I thought one of the key reasons for choosing a permissive license rather than something like GPL was to encourage manufacturers to use the project in their own products, encouraging interoperability.  If this is the case then there has to be a reference hardware design that is absolute lowest cost.

Agreed, though it might not have to be this next V0.2 revision, where actual energy-saving ability has yet to be established and ease of tweaking is still useful for us, and to lure in a wider pool of early adopters.

> Using a hobbyist platform is likely to be off-putting as well, I therefore think that vanilla AVR is a good compromise, especially since the three of us here with AVR experience all prefer to work bare-metal anyway.  There is then nothing stopping us from doing a super-set reference platform with a more capacious AVR and the Arduino bootloader pre-loaded.

Agreed.

> A cost-reduced platform (wired interfaces aside) would boil down to the AVR, radio, H-bridge and encoder, thermistor, and maybe a couple of buttons.  There isn't really a need for an external RTC since this can be implemented in software still with uA average power consumption, and it is even debatable whether the expense of a digital temperature sensor can be justified when a) it might not actually be any more accurate, b) we already talked about the UI being simply "I'm too hot" and "I'm too cold", in which case absolute accuracy isn't really that important.

Mr Margolis was not convinced that we'd get away without an external RTC if we really minimise power consumption, but I do want to actually experiment to establish this one way or another.

Absolute accuracy may be important if (a) the thing is to "just work" off the shelf for end users and (b) to minimise heating energy use, but that might be something that we could establish during a DECC trial for example.  For the moment I'd prefer good basic accuracy and then simulate some inaccuracy during trials to see what matters.  In any case we need some decent precision for holding a steady set-point I suspect.

> I have been hacking at my Eurotronic Comet, by the way, but I will write about that in a separate post...

Good!  Looking forward to it.

My task for the rest of this afternoon is to try to wire up and test a new MCP79410: it's going to be a nightmare!  B^>

Rgds

Damon