A beginners adventure into the world of multirotor fpv drone racing and freestyle

R-XSR no receiver output in Betaflight

Problem: Have telemetry but Betaflight shows no stick input in receiver tab.

Details: Put a quad back together but no stick input in Betaflight receiver tab. 

- Verified SBUS connection
- Flashed TX with new firmware
- Flashed to latest stable Betaflight
- Tried second, new R-XSR
- Flashed R-XSR to fport
- Still no input!!

fc:  Bardwell F4 (CLRACING4 Target)
Bf:  Betaflight 4.1.2
rx:  Frsky R-XSR
tx:  Frsky QX7

Solution: Verify your R-XSR has a blue light in addition to the green bound light. If you hold the R-XSR bind button for too long it will switch from SBUS to CPPM mode !

If there is no blue light, long hold the bind button and release and the blue light should appear. This means it is in SBUS mode.

Hopefully blogging this will prevent me from wasting several hours again !

Betaflight SD card Blackbox problems ( Fatal error Reboot to retry)

Problem: SD card section in blackbox menu states: Fatal error Reboot to retry


fc: Matek F722-SE
Bf: Betaflight 4.0.4
rx: Frsky R-XSR
tx: Frsky x-lite
vtx: RDQ Mach 1
vrx: FatShark Scout

Solution: Your SD card needs a valid FAT32 partition in order for Betaflight to recognize it and use it for black box.

To see if this is your problem:

  • Betaflight CLI
    • sd_info
  • If the card is detected by Betaflight (shows manufacturer, size, etc) but error message is ‘no FAT MBR partitions‘ – it is because you need a FAT32 partition on your card
  • exFAT and NTFS volumes cannot b read by flight controllers in Betaflight (at this time)


Default Windows behaviour does not allow you to create a FAT32 volume larger than 4 GB. There are two sets of instructions. One is if you have a card 4GB or smaller and can use Windows disk utilities and the other is a small 3rd party tool that can quickly format a much larger FAT32 partition for you.

First make sure there is nothing valuable on the card!

  • Remove SD card from flight controller and mount it to your Windows PC (via USB, or SD slot if you have it)
  • Run -> diskmgr
  • Select your SD card from list of disks in Windows
  • Right click any existing volumes
  • Delete volumes until there are no volumes on the SD card
What your SD card should look like after removing all of the volumes.

If you have a 4GB card or lower:

  • Right click unallocated space
  • Create a ‘New Simple Volume’
  • Use 4096MB as the volume size
Make the volume 4096 MB (4GB in size)
  • Select file system as FAT32 using drop down
  • If FAT32 is not an option, go back and make sure that your volume size is not over 4096 MB!
Format as FAT32

If you have a greater than 4GB card:


  • Put SD card into flight controller
  • Open Betaflight
  • CLI
    • sd_info
  • Filesystem: Ready indicates things are fine or Filesystem: Initialize and returning to Ready after
Card is detected and file system is ready for your black box logs!
  • If Filesystem: Initialize is taking a long time
    • Betaflight CLI – sd_card dma = off
    • Change Blackbox logging rate down to 4 kHz or less
    • These two changes worked for me
What Betaflight should look like when the card is ready.

With all of this, you should be ready to go ! Hopefully larger volumes will be able to be used in the future, but this is quite common with these type of boards – ie a Raspberry pi expects to be booted off of a FAT32 volume.

Matek F722-SE Betaflight 4 Camera Control and SmartPort

Problem: Camera control and SmartPort telemetry not functioning (on soft serial) with Matek F722-SE flight controller and Betaflight 4.04.


fc:  Matek F722-SE  
Bf:  Betaflight 4.0.4
rx:  Frsky R-XSR
tx:  Frsky x-lite
vtx: RDQ Mach 1 
vrx: FatShark Scout

As a new build and new to this hobby, I am going to put this under troubleshooting as well as setup. I had trouble getting my Runcam OSD camera control and Frsky SmartPort telemetry working.

Camera control:

The Matek manual states that the RX4 pad has a 200ohm resistor and can be remapped to camera control. The instructions are to assign it via the Betaflight CLI and set it up under the ports tab.

Solution: Make sure that nothing else is assigned to this resource before assigning camera control to UART 4 RX.

Open Matek pin definitions for reference: http://www.mateksys.com/?portfolio=f722-se#tab-id-7

  • Open Betaflight
  • In CLI:
    • resource (lists all resources and their allocations)
  • SERIAL_RX 4 and resource PWM 2 are on A01 and need to be unassigned
  • In CLI:
    • resource SERIAL_RX 4 none
    • resource PWM 2 none
  • Can now assign camera control without any conflicts
  • In CLI:
    • resource camera_control 1 A01
    • save
  • Reboot
  • Camera control should now work in OSD!

SmartPort (softserial)

Similarly to camera control, the manual states that TX2 can be used for SmartPort with softserial -OR- use another UART TX (as the board has built in inversion). The softserial option is so you can free up that UART you otherwise would have used for SmartPort.

Solution: Make sure that Serial RX / PWM is not assigned to this resource before assigning camera control to UART 4 – OR – use another (closeby?) UART – ie UART 1 TX.

  • Open Betaflight
  • Configuration menu: Enable Soft Serial
  • Reboot
  • In CLI:
    • resource (lists all resources and their allocations)
  • SERIAL_TX 2 and resource PWM 1 are on A02. and need to be unassigned
  • In CLI:
    • resource SERIAL_TX 2 none
    • resource PWM 1 none
  • Can now assign soft serial without any conflicts
  • In CLI:
    • resource serial_tx 11 A02
    • save
  • Reboot
  • Ports menu: Assign SmartPort on SOFTSERIAL1 via dropdown
  • Reboot

Perhaps all of this is obvious to people that have been around longer, but this was definitely a good introduction to resource assignment on flight controllers !

Betaflight RSSI flashing zero in OSD (Part Two – The Real Solution)

Problem: RSSI flashing 0 (incorrect) in goggles using Betaflight OSD.


fc:  Matek F722-SE  
Bf:  Betaflight 4.0.4
rx:  Frsky R-XSR
tx:  Frsky x-lite
vtx: RDQ Mach 1 
vrx: FatShark Scout

Out of the box, I was having the same issue on my new Matek F722-SE as I had on the JB flight controller with the RSSI value flashing zero in the OSD. After some fiddling, turns out that the solution is to send the RSSI data from your transmitter back to the FC and out via the Beta Flight OSD.

Solution: Create a new input on transmitter mapped to RSSI signal, create mix and configure flight controller in Betaflight to use this new AUX input as your RSSI channel.

  • Use OpenTX Companion OR use Radio
  • Edit Model
  • Create a new input (named whatever you want)
  • Map input to RSSI from telemetry
  • Change scale to 100
  • Change weight to 100
In OpenTX Companion
In OpenTX on Frsky X-lite (Note: the 100.0 which is the RSSI strength from telemetry)
  • Select a free channel and create a new mix
  • Map mix to input created above
  • Change weight to +200% and Offset to -100%
In Companion
Again on the transmitter
  • Connect quad to PC
  • Open Betaflight
  • Go to Receiver menu
  • Check your list of inputs and find the RSSI input
    • RTEA are CH 1-4
    • CH5 is AUX1, CH6 is AUX2, CH7 is AUX3 and so on
    • In my case I put RSSI on CH10 which is AUX 6
  • Change RSSI Channel drop down to the AUX channel of your RSSI input
  • Save and reboot
AUX 6 (CH10) is the input transmitting the RSSI signal from my radio