Getting RSSI value real time?

I have cuav p9 telemetry which uses p900 radio module. I connected this telemetry module to my PCs via USB. I don’t use it with flight control unit. I wonder how to get RSSI value that the LED indicates on telemetry real time to software?

If it supports MavLink just listen for the packet with the data IIRC RADIO_STATUS or something like that. Otherwise tough luck unless it has two serials with one for configuration or some other RSSI output.