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I have a have a dbus-driver which publishes data from my pv inverter to the dbus via a dbus-service derived from dummy-service.
How can I read dbus values, e.g. the current battery charging power (from com.victronenergy.system?). How can I write other dbus values, e.g. the limited the charging power of the battery?
If you are smart enough to write a drive to publish values, reading values should be straightforward. All the information is available here:
https://github.com/victronenergy/venus/wiki/dbus-api
And use dbus-spy to inspect the dbus in real time.
Hi @dcsonka as most of the "answer" information in this thread is inside comments, I hereby try to write up a complete answer.
How can I read dbus values, e.g. the current battery charging power (from com.victronenergy.system?).
I know of two ways, Victron provides this functionality in Python:
The latter - as far as I understand the documentation - is the preferred option (as it handles a lot of overhead for you).
How can I write other dbus values, e.g. the limited the charging power of the battery?
When you found out on how to read the values via "DbusMonitor" you could use the same mechanism to also write these values.
However, in my understanding it would be better to create a "Battery Monitor" and you publish your CVL, CCL, DCL etc. values via your driver (inside your own namespace). Then the Venus OS would pick up your driver's values and publish them throughout the system. With this approach you would only need to write in your own namespace/service and not mess with any other processes. This is actually what the Battery Aggregator and dbus-serialdriver (among others) do.
For this you need to use the namespace "com.victronenergy.battery" and need to publish a couple of "/Info" paths/values (see dbus battery parameters and use "dbus-spy" to look at the values on a live system). Then you might want to enable DVCC and the chargers (if connected to Venus OS) will then use the parameters you previously published.
The above is what I did. There might be different approaches. And your scenario or use case might be different. My answer is based on what what you wrote and what I know. Hopefully this helps. Otherwise please you could provide more information on your setup and requirements.
I am also interested in how to read the temperature sensors values with a python script?
I can do it with dbus, but I want to read the same through a python script. How can I achieve the same through python?
root@einstein:~# dbus -y com.victronenergy.temperature.adc_builtin0_7 /Temperature GetValue
value = 19
You have multiple options, direct access to dbus, MQTT and ModTCP, using MQTT might be easier. It depends on where you want your code to run. If you gave a Cerbo, enabling the noce-red via Venus OS Large is problem the most simplest.
https://www.victronenergy.com/live/ccgx:modbustcp_faq
https://github.com/victronenergy/venus/wiki/dbus-api
https://github.com/victronenergy/dbus-mqtt
For reading data from other processes as your service, see description here: https://github.com/victronenergy/velib_python
Use VeDbusItemImport to read a single value from other processes the dbus, and monitor its signals. Use DbusMonitor to monitor multiple values from other processes
See https://github.com/victronenergy/velib_python/blob/master/examples/vedbusitem_import_examples.py for an example with VeDbusItemImport. But DbusMonitor is probably preferred.
Unfortunately I get for the command "dbus -y com.victronenergy.system/Dc/Battery/Soc GetValue" an empty output. Do I have to configure something before?
If you have ssh'ed into GX device, type dbus-spy to view the paths and values available. On my test device the Battery SOC reported by a BMV-702 is at
com.victronenergy.battery.ttyO2/Soc
dbus -y com.victronenergy.system /Dc/Battery/Soc GetValue
You need to insert a SPACE character (" ") between the service name ("com.victronenergy.system") and the path ("/Dc/Battery/Soc").
