Reading VBus data from Sonnenkraft SKSC2 via USB port (raspberry pi w/ linux distro)

[Eduardo Cunha]

Hello,

I'm trying to read VBus data from a solar heater (Sonnenkraft SKSC2) and my current setup is just a simple 2-wire cable connecting the Vbus interface to a USB (RS485) converter (https://pt.aliexpress.com/item/1956981483.html?spm=2114.13010608.0.0.lfrBZY&gatewayAdapt=glo2bra), which is connected to my pc. The image below shows the 2-wire cable connected to the VBus interface.



I tried to test the example in the documentation for RESOL-Vbus (http://danielwippermann.github.io/resol-vbus/#/md/examples/json-live-data-server/README) and I changed the config file appropriately, i.e., "connectionClassName: 'SerialConnection'" and "path: '/dev/ttyUSB0'", but I got an empty json file as the output.

The output on the terminal is the following:
debug: Starting server...
debug: Connect to VBus data source...
info: Ready to serve from the following URLs:
info:     - http://127.0.0.1:3333/api/v1/live-data (internal)
info:     - http://192.168.1.109:3333/api/v1/live-data
debug: HeaderSet complete
debug: HeaderSet complete
debug: HeaderSet complete

I tested the connection via minicom with "minicom -D /dev/ttyUSB0 -b 9600" and got this result:

I suppose the flow of data in minicom should be constant, but what you see in the picture is how it is statically, i.e., no more characters appear. It seems like a baudrate mismatch, but I tried other rates and it didn't work either (19200, 38400, 57600, 115200).

I thank you in advance for your time and for helping me regarding this issue.

Best regards,
Eduardo Cunha

[Eduardo Cunha]

The last image is missing, here it is:

[Dave Liquorice]

On Mon 11 Dec 2023 19:30, Eduardo Cunha wrote:
> I'm trying to read VBus data from a solar heater (Sonnenkraft SKSC2)
> and my current setup is just a simple 2-wire cable connecting the
> Vbus interface to a USB (RS485) converter

Are you sure that the Sonnekraft is using RS485? That should be a
balanced and differential signal on a twisted pair of wires. Resol had
(have?) a habit of calling things "V-Bus" which should be RS485 but
actually implementing it with a roughly 8 V unbalanced data stream.
RS485 it ain't.

I was only interested in logging the data stream on a Raspberry Pi and
simple 1 transistor circuit made the 8 V "Pi safe". Circuit in the forum
somewhere.

--
Cheers
Dave.