Hello. I owe you an apologize. I made a mistake. I omitted the device's name "RUTX11" when I did answer. Thinking all the time we were talking about RUT955.
Currently our other routers does not have a functionality to measure their power supply voltage because there is no internal circuitry to measure how much the voltage input is.
The only device that can, in some way, measure analog voltage is the RUT955 because it does have an analog input. the workaround is to connect the analog input to the power supply and measure the analog input using the command cat /sys/class/hwmon/hwmon0/device/in0_input
In the case of the JSON-RPC feature. It will be implemented in the following updates.
Please keep tuned via https://teltonika-iot-group.com/subscribe/ for new implementations.