Getting FRsky telemetry on the Revo is abit of a challenge as the board itself does not have a serial inverter which is required for FRsky smartport. You can make your own one
The other option is to do some soldering to send the serial data to a pin specifically on your Frsky receiver so that it does not need to be inverted, a guide for doing that on an X4R is here
The last option is to wait for softserial to be added to betaflight so then you can due software emulated serial port which can be inverted via software. This should be released soon
But its much easier to either use an OSD to get info, or hook up a OPlink module to get a telemetry stream that way as the original openpilot Revo boards already include a OPlink module on them, so you just need one for the ground.