I have an old XM+ receiver that does not do RSSI. Some of the newer ones come with RSSI set up on a channel. How can I set up RSSI to be on a certain channel?

• I'm not sure I understand the question? Both will have both a receiver and a transmitter and therefore can communicate? Apr 23 '20 at 20:56
• "Why can't a basic receiver do telemetry?"... Uh, they can. Even the most bargain-basement FlySky ia6 PWM receiver can handle certain telemetry functions.
– ifconfig
Apr 23 '20 at 21:03
• I think this question would be thoughtfully answerable if we are discussing a specific "basic receiver" which doesn't have telemetry support.
– ifconfig
Apr 23 '20 at 21:04
• @ifconfig, I have changed the question to make it more specific.
– Jacob B
Apr 23 '20 at 21:13

For the sake of the random visitor I must first point out that the XM and XM+ receivers do not include telemetry, as in they don't transmit anything back to your remote over the radio link. What the XM/XM+ do offer, however, is an onboard RSSI readout, i.e. supplying RSSI information directly to the flight controller.

You can solder a wire to this pad, and it will output the RSSI value as a voltage which can then be read by your flight controller via an ADC pin (usually labeled RSSI). This feature is, as far as I know, always on.

The second, which is the one you're asking about, is transmitting the RSSI readout as one of the RC channels, either channel 8 or channel 16.

To enable the latter option (if it's not enabled) or change the channel, you'll have to flash the corresponding firmware to the receiver. If you go to the FrSky site, to the page that offers firmwares for your receiver, and download the archive, you'll see six files, labeled something like:

XM+FCC170313.frk
XM+LBT170313.frk