This is the version 2.5 firmware released summer 2013
together with the version 7 hardware.
(this version firmware is offcourse also compatible with older RX, and they can all be user upgraded)
This is just one of several debug modes available to the advanced user.
The live display of channels versus errors on channels. are explained in this video.
you dont need PC connection to capture any data while flying,
Land, then connect to pc via serial port (usb converter) and the graph will be showed if enabled.
Reboot the RX to zero all values.
You can also capture the serial data WHILE flying using a serial logger,
and then later analyze it via height and distance. (we dont make or sell data loggers for this, but sparkfun do)