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

[Stuart Poulton]

> So, the question here, in my mind, is what is the power overhead of having a USB interface as "dead weight" in the AVR as opposed to perhaps an FTDI chip that's only powered from the USB bus when connected?

I know you can get the ATMEGA32U4 (same chip as a lenoardo) down to 0.04mA

>> Unfortunately all three radio modules now seem to be end of life.
> 
> Hmm. will have to keep an eye out for an alternative.

Some details about the EOL of some RFM products here 

http://blog.homelabs.org.uk/rfm12b-end-of-life/

> 
> 1) AVR with built-in USB
> 2) AVR with USB-to-Serial chip
> 3) AVR only, and use a cable containing a USB-to-Serial chip
> 
> Option 1 being preferable, IMHO, especially as it opens up the possibility to do more with the USB interface. Maybe a PC application to program the schedule on the device, for example?
> 
> I've heard the AVRs with built-in USB can be a pain during development, though, because the USB interface goes down every time you reset the CPU after a download. This is the reason devices like the UNO have a separate CPU to provide the USB link, so both of your modules sound useful, perhaps at different stages in the development.

I've been thinking about this, USB adds to the cost of a chip, yet allows for more configurability, I think I'm moving toward a model where USB and RF are used, so USB + Power for those TRV's where it's possible to cable, RF + Battery for those where cabling isn't possible.

Stuart
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