[OpenTRV-dev] Dongle

[Tristan Keen]

  Thanks to all your help - though I'd already ordered an Adafruit RFM69HCW
868 MHz "Bonnet" for my Raspberry Pi (from Pimoroni), on the strength of a
Hope datasheet suggesting it was an easy replacement part.

  Unfortunately while the pinout might be the same, the registers are
totally different so it's been slow going; especially when I realised
Manchester encoding is implemented completely differently between the two -
I was about to give up & buy a new module. Luckily, despite
https://github.com/opentrv/OTRadioLink/blob/345b45f9df92eac78caa483d4230a11bde21d7d8/content/OTRadioLink/utility/OTRFM23BLink_OTRFM23BLink.cpp#L787
your
(Christoph's) config actually shows Manchester was turned off.  Trying that
as a last-gasp effort seems to work - I can now receive valid secure frames
with sensible IDs matching some of the hex printed inside the Radbots, and
incrementing message_counters from the trailer.

  Now to read up on the encryption approach & get that working in Python,
then I'll try reprogramming the key on one of the radbots to a known
value.  Yes, my current code is similarly littered with odd notes, some
copied in material and private IDs, I'll clean it up a bit & clone it
publically when I've got my MVP working.

Thanks,
Tristan.


On Thu, 7 Jan 2021 at 19:23, Damon Hart-Davis <dhd at exnet.com> wrote:

> Purged of third-party copyright material, would you consider adding that
> to an appropriate place in our Wiki or one of the GitHub repos?
>
> Good to have register settings for another radio widely available (and the
> Pi stuff)!
>
> Note that there is one non-JSON data item in there, the valve %, which is
> a single binary byte easy for a boiler controller with a small MCU to use...
>
> Rgds
>
> Damon
>
>
> On 7 Jan 2021, at 19:14, christoph at winterstiger.at wrote:
>
> Hi Tristan,
>
> That’s right, I have this working. I played around with multiple different
> modules and I think the cheapest option is a TI CC1101-based module (lots
> of options for under GBP 10 on eBay). Most of them come with antennas that
> should work fine for development purposes if you’re in the same room as the
> RadBot.
>
> That module (and many similar ones) uses the SPI-bus for communication,
> which is very easy to use on an RPI, and there are also options for other
> platforms, e.g. CH431A-based modules (but I haven’t tried those yet). This
> takes voltage + ground + 4 SPI wires + 1 interrupt wire (interrupts when
> the module received a packet). On the RPI, no other hardware is required
> and I think a CH431A wouldn’t need any other external components either.
>
> For my own experiments I wrote a monitoring app that lets me configure the
> module on the fly so I can play around with all those RF-related options,
> but I foolishly copied a bunch of copyrighted text from the various
> datasheets into it, so now I’ll have to remove that before I can publish
> it. I attached the RadBot config I use, which gives you all the register
> settings for the CC1101. Once all the registers are set, you just need an
> event handler for rising edges on the interrupt lines to get the raw
> packets. Those are encrypted by the RadBot with a pre-set key, so they need
> to be decrypted. Once that is done, the actual data decoding is trivial as
> it’s just a simple JSON object.
>
> I’ll try to find some time over this or the next weekend to clean up my
> code so I can publish it.
>
> Cheers,
> Christoph
>
> *From:* OpenTRV-dev <opentrv-dev-bounces at lists.opentrv.org.uk> *On Behalf
> Of *Tristan Keen
> *Sent:* 30 December 2020 10:33
> *To:* opentrv-dev at lists.opentrv.org.uk
> *Subject:* Re: [OpenTRV-dev] Dongle
>
> Hi Christoph,
>
> I read from the mailing-list archives that you recently managed to "...
> receive the messages on a raspberry pi with a cheapo 868Mhz transceiver and
> it works fairly reliably".
>
> Would it be possible to share a bit more detail on what actual transceiver
> you used with what Pi, plus any other hardware mods you had to make?
> Additionally the code you used to decode the messages - even in partial
> form if you prefer. I'm an experienced developer with some hardware
> knowledge, so anything rough would still be gratefully received.
>
> I'm trying to make up something similar to the Stats Hub to collect
> information broadcast by the OpenTRV/Radbots, but without building so much
> custom hardware if possible...
>
> Thanks in advance,
> Tristan Keen.
>
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