Wired setup?

[Lukas Barth]

Hi everyone,

I have an HR20 (style) thermostat and want to flash it with openHR20, hook it up to an Arduino and control it from that Arduino. I do not want the wireless interface - in my opinion, a wired connection is better if you don't mind the cables, which I don't.

Now the question is: Is that possible out-of-the-box? I tried looking at the software, but my low-level-C is not good enough, I'm afraid. The basic questions are:

- Does openHR20 expose a serial console somewhere? On the pins of the JTAG header? Or would the only possibility be to grab the console at the points that are usually connected to the wireless module?

- Does openHR20 work at all if no wireless module is present? I figure that this wireless module is configurable (for different frequencies?), so openHR20 probably expects some responses from the module.. does it crash if the module is not present?

Thanks a lot,

Lukas

[Tomas Kopal]

Hi,

it >should< be possible.

Hardware-wise, the connector you are referring to as JTAG header
contains also serial port (pins TXD and RXD plus GND) which you can use
to connect to arduino. For short cable, you can connect directly (with
level shifter for classic arduino with 5V logic, directly with 3.3V
clones). For longer cable you may have to add some amplification (bus
driver, convertor etc). For details, see the documents in the git
repository. Some people are using this with rs-232 to rs-485 converter
and serial bus for multiple thermostats, AFAIK.

Software-wise, it should be possible to disable RFM module by define
(RFM=0) and enable the serial port (defines COM_RS232 or COM_RS485).
Please check the makefiles.

I don't think there is any software for serial control on arduino, but
you can check the php scripts in the frontend folder for inspiration how
to use the protocol. It might be a good idea to start with connecting
the serial to a PC (via level shifter, PC does not have 3.3V serial !),
with terminal first and verify the connection works.

I haven't tested this personally, so take this with a grain of salt :-).

Good luck and report back...

Tomas