Oh My…
That’s not what you want to see cruising over a river half a mile from home. Poor video signal is pretty plain to see, there’s so much information being exchanged between the video transmitter and receiver pair that even the slightest bit of signal loss will manifest itself as evident video breakup. However, signal loss between the radio transmitter and receiver is more difficult to detect, usually only becoming noticeable when a failsafe occurs. Setting up RSSI readouts with your FrSky receiver is an excellent way to keep track of your radio link quality.[vc_row][vc_column width=”1/4″][/vc_column][vc_column width=”1/2″][vc_single_image image=”2051″ img_size=”full” alignment=”center” onclick=”link_image” image_hovers=”false”][/vc_column][vc_column width=”1/4″][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]
What is RSSI?
RSSI (Received Signal Strength Indicator) is a measurement of the signal strength between a radio receiver and transmitter pair. The unit for RSSI is decibels (dB), decibels are used to quantify the power of an electrical signal.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]
Can my Receiver Output RSSI Information?
This guide will focus on using Betaflight/Butterflight in conjunction with FrSky ‘R’ (X8R, X4R-SB, XSR, R-XSR) and ‘M’ (XM, XM+) receivers. Displaying RSSI values within Betaflight OSD will also be covered. The Taranis X9D+ will be the model of choice for this tutorial, although other FrSky radios such as the QX7 follow similar setup processes.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column width=”1/4″][/vc_column][vc_column width=”1/2″][vc_single_image image=”1313″ img_size=”full” alignment=”center” onclick=”link_image” image_hovers=”false”][/vc_column][vc_column width=”1/4″][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]
Two Types of FrSky Telemetry Output
There are two distinct variations of FrSky telemetry output: Smartport and channel transmission. ‘R’ receivers utilise Smartport technology, all telemetry values including RSSI are exchanged via a single wire connected to a hardware UART. ‘M’ receivers are designed to communicate RSSI values by a defined output channel, for both the XM and XM+ receivers, Channel 16 is reserved for RSSI outputs.[/vc_column_text][vc_column_text]Please note that this guide does not describe the receiver binding process, consult your receiver manual for more information.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column width=”1/2″][vc_single_image image=”1322″ img_size=”full” alignment=”center” onclick=”link_image” image_hovers=”false”][/vc_column][vc_column width=”1/2″][vc_single_image image=”1328″ img_size=”full” alignment=”center” onclick=”link_image” image_hovers=”false”][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]
‘R’ Receiver Configuration
Let’s start with the ‘R’ receivers, specifically the XSR. The wiring process for all R receivers is near identical, likewise for the ‘M’ line. Smartport is a two-way signal that allows for information to be sent and received along a singular wire, making the wiring process more efficient. Firstly, identify the smartport wire from your receiver and connect it to an unused ‘TX’ (transmit) pad or pin on the flight controller. [/vc_column_text][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]With the wiring out of the way, open up the Betaflight/Butterflight configurator and navigate to the ports tab. Find the unique UART that the Smartport wire was assigned to and select “Smartport” from the dropdown menu. Remember to press save, then continue to the configuration window.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column][vc_single_image image=”2049″ img_size=”full” alignment=”center” onclick=”link_image” image_hovers=”false”][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]In the configuration window, locate the ‘Other Features Menu’ and ensure that the ‘Telemetry’ button is activated. Don’t forget to save and reboot or you will lose your changes. With this process completed, disconnect from the Betaflight/Butterflight configurator and get out your Taranis.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column][vc_single_image image=”2040″ img_size=”full” alignment=”center” onclick=”link_image” image_hovers=”false”][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]Open up the Taranis menu with the ‘MENU’ key, long-press the ‘PAGE’ button twice to navigate to the telemetry page. Once in the telemetry page, turn on your quadcopter and press the ‘Discover new sensors’ button to allow the Taranis to automatically identify the RSSI output. Once the RSSI value becomes visible in the sensors list, advance onward to the next step.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column width=”1/4″][/vc_column][vc_column width=”1/2″][vc_single_image image=”2043″ img_size=”full” alignment=”center” onclick=”link_image” image_hovers=”false”][/vc_column][vc_column width=”1/4″][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]Now you must decide how you want your radio to communicate RSSI information. There are three methods; on-screen telemetry, callouts or OSD. (The OSD technique is covered at the end of the ‘M’ receiver tutorial).[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]
On-Screen Telemetry
On-screen telemetry allows for the display of RSSI values on the screen of the Taranis. To configure this, press ‘MENU’ once and long-press the ‘PAGE’ button to enter the ‘DISPLAY’ menu. In the ‘DISPLAY’ page, select the ‘None’ option next to an available screen and change it to ‘Nums’ or ‘Bars’. Now, select one of the available ‘—’ spaces and scroll through the menu until RSSI is found, press enter and exit the menu. RSSI values can now be displayed by long-pressing the page button outside of the menu.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column width=”1/2″][vc_single_image image=”2041″ img_size=”full” alignment=”center” onclick=”link_image” image_hovers=”false”][/vc_column][vc_column width=”1/2″][vc_single_image image=”2045″ img_size=”full” alignment=”center” onclick=”link_image” image_hovers=”false”][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]
Callouts
Press ‘MENU’ once and long-press the ‘PAGE’ button four times over. In the ‘SPECIAL FUNCTIONS’ page, select a free ‘SF’ profile. Firstly assign it to a switch than choose the ‘Play Value’ option in the next selection. Now, select RSSI as the value and choose a suitable callout period. The FrSky radio can now audibly read RSSI values in live time.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column width=”1/4″][/vc_column][vc_column width=”1/2″][vc_single_image image=”2044″ img_size=”full” alignment=”center” onclick=”link_image” image_hovers=”false”][/vc_column][vc_column width=”1/4″][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]
‘M’ Receiver Configuration
‘M’ receiver RSSI can be displayed in the Betaflight OSD. As mentioned before, RSSI information is transmitted on Channel 16 by SBUS communication, making wiring extremely simple. Locate the SBUS wire on the XM or XM+ receiver and route it to a free UART RX (receive) pin or pad on the flight controller.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]Connect the flight controller to the Betaflight/Butterflight configurator and open the ports tab. Now, find the UART number that SBUS was designated to and activate the Serial RX button. Press save.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column][vc_single_image image=”2048″ img_size=”full” alignment=”center” onclick=”link_image” image_hovers=”false”][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]Head over to the configuration tab and find the ‘Receiver’ menu, select ‘Serial-Based receiver from the first dropdown and choose ‘SBUS’ in the second dropdown window. Remember to save and reboot the flight controller.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column][vc_single_image image=”2039″ img_size=”full” alignment=”center” onclick=”link_image” image_hovers=”false”][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]Power up your ‘M’ receiver and FrSky radio, confirm that all channels are responding correctly. AUX 12 should be indicating a higher value than the other channels, this is the RSSI channel. (Four movement channels + twelve AUX channels = sixteen) In the ‘RSSI Channel’ dropdown, choose AUX 12. Now, the RSSI value can be set to display in the Betaflight OSD.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column][vc_single_image image=”2050″ img_size=”full” alignment=”center” onclick=”link_image” image_hovers=”false”][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]Placing RSSI values in the Betaflight OSD is very simple, enter the OSD tab and activate the ‘RSSI Value’ button under ‘Elements’. Position the RSSI indicator anywhere on the OSD display and press save. That’s it! You can now view the real-time RSSI strength in your goggles.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column][vc_single_image image=”2047″ img_size=”full” alignment=”center” onclick=”link_image” image_hovers=”false”][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]
Conclusion
RSSI is a very useful tool not only for those going the distance, but also freestyle and race FPV drone pilots. RSSI can also be used to test the radio frequency situation of an environment before attempting any risky manoeuvres, or even to find a lost FPV drone. It’s highly recommended that you enable RSSI monitoring today.[/vc_column_text][/vc_column][/vc_row]
Dude!!! This was so insanely helpful. Thanks a ton for the read.
What about channel 8/aux 4, for sending rssi over a channel? Some only config taranis for 8 channels, max.
Useful info for scaling the rssi from the xm
If its a quad with Betaflight: When the RX does output RSSI, start Betaflight, go to receiver tab, select Aux4 as RSSI channel (or Aux12 if 16CH firmware) and active RSSI in OSD. Move it on the screen. When it shows and are correct you will most likely find that the signal scale are from 62-99%, and signal loss happen below 66-68%. Set RSSI alarm to 70% and be happy. If you want to have more of a scale go in to CLI:
set rssi_scale = 180
set rssi_offset = -100
set osd_rssi_alarm = 25
save
I did everything here and in my receiver tab, aux 13 and 14 are showing low values.
I am missing how to display rssi information for XM in the radio
Me too… 🙁
Did everything like shown, but still not RSSI … R-XSR and Taranis QX7….no way to discover new sensors(rssi)..
I connect smartport to TX3 (OmnibusF4) …still no Rssi to find…… I have 2 wizzard220s -2 QX7- 2 R-XSR and still no way…. , any idea???
I have read that also the new deliveries of R-XSR want new firmware for telemetri and Sbus in only one wire. Is this so? Why?