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

Thu Apr 4 12:00:13 BST 2013

> ----------------original message-----------------
> To: "Closed list for developer discussions"
> Date: Thu, 4 Apr 2013 11:05:37 +0100 (BST)
> -------------------------------------------------
>> Apologies for the delay.
>> I've actually been thinking about what would make an ideal boiler /
>> valve
>> control node for me. On the basis that (hopefully!) the weather won't
>> call
>> for heating too much longer, and that my current tank thermostat keeps
>> arcing, that might be a good place to do "summer hacking" for me.
>> I have got round to having a look into the RFM12Pi. It's basically an
>> ATTINY84 with an RFM12 connected to the SPI and it bit-bashes serial
>> data
>> to and from the Pi on 2 other Io pins. 3 spare pins are brought out to a
>> 3
>> pin header so I guess these could be employed to drive valves. It might
>> also be possible to read Onewire temperature sensors on one of the spare
>> pins, I guess. The serial protocol is a very simple human-readable ascii
>> command driven affair, so I don't see a problem with extending that.
>> I keep wondering if a very simple node talking to a Pi, which can give
>> me
>> web access to set the schedules, etc. is what I want or whether this
>> should be a more autonomous "boiler programmer" with "advance" buttons,
>> scheduler, RTC and maybe even a user interface to program it manually.
>> I keep think that the RFM12Pi is a bit too minimal to cope with what I
>> might want to throw at it. I might build something around a more
>> powerful
>> AVR, containing some switching for the valves, and see where that takes
>> me.
>> I wonder if I should still connect it to a Pi, or give it an ethernet
>> interface?
>> Kevin
> Hi Kevin,
> I have designed a dual-RFM23B board for the Pi which has an optional
> 1-wire interface. Prototype PCBs are on their way from China as we speak.
> Assuming it all works properly I'll release the design and should have a
> few for sale in about a month, so maybe this would be of interest to you?
> I'll price it up when I get in this evening.
> Feature summary as follows:
> - 1x RFM22B/RFM23B at 868 MHz
> - 1x optional RFM22B/RFM23B at 433 MHz
> - I2C to 1-wire bridge
> - Real-time clock with lithium battery backup
> - ATMEGA328 with serial connection to Pi, SPI bus master for TRXs
> - Bus routing logic to enable the Pi to be SPI bus master. This allows the
> Pi to program the AVR without an external programmer, and also to
> communicate directly with the TRXs.
> I have also done some work on a standalone ethernet/RFM23 bridge board
> based on ARM Cortex M4, but I will probably keep this on hold pending some
> clarification of the future availability of the HopeRF modules.
> Mike

Hi Mike,

That does sound very interesting. A ready-made board would allow me to
concentrate on some code.


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