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

[Damon Hart-Davis]

Hi!

On 1 Apr 2013, at 09:35, Kevin Wood wrote:

> Hi Damon,
> 
> A few musings on using an AVR...
> 
> It might be worth a read of the notes here if you haven't come across it:
> 
> http://openenergymonitor.org/emon/emontx
> 

That's definitely in the right sort of territory, at 3.3V rather than 5V for example, though I'd like us to be immediately battery-operable, eg ~2.2V for 2XAA rechargeables.

> No personal experience but a similar beast based loosely on an Uno. There are some notes about optimisation of power consumption there which might be worth a read.

I'll look at those notes, thanks!

> 
> I've never used an Arduino but I've used AVR devices quite extensively using just the GNU toolchain, AVR Libc and AVRDude to program them using an STK500. Arduino adds a nice development environment and a boot loader to allow the chip to be programmed through USB / RS232, as I understand it. I must pick up an Arduino and have a play sometime.

In effect it is the bootloader I'd like to add for maximum ease of (re)programming, though maybe I can be talked out of it.

> Unfortunately I don't know a lot about PICAXE.

Not a problem.  It seems to me to be the next-largest uC community after the Arduino: I just happened to get to it first!

> There are a couple of AVR libraries around to drive the RFM12. I did try to get one working with the RFM01 and RFM02 but the latter devices are a real pain to drive in comparison to the RFM12 and I haven't (yet!) cracked them. I think an RFM12 will connect straight to the I2C pins on port B of the 328.

We are currently using the RFM22/RFM23 since the RFM12 is not able to talk to the FHT8V (Conrad/ELV/eQ-e) wireless valves that we are currently using.

Unfortunately all three radio modules now seem to be end of life.

> 
> I've got some C code that drives Dallas 1wire temperature sensors from an AVR, by the way. I use that in an AVR based PID controller I made for my home brewery.

The current design uses the DS18B20, but its operating voltage is not low enough for 2xAA.

> The UNO has a separate AVR handling the serial port. I wonder how easily the power supplies to this can be separated from that to the AVR device running the "user code", as this will no doubt affect the current consumption adversely. It might be that it'd be best to knock up a board or two with an ATMega328, RFM12, Onewire device, etc. and use the UNO to program it?

This is the sort of area I am not at all sure about.  The Leonardo's uC has the USB built-in, and thus may save board area and power consumption ultimately.

Rgds

Damon