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Help! RX won't communicate with FC

#1
Hello!
I am fairly new to the building of multirotors, this build being my second, so maybe I am just missing some little piece that you experienced people can point out. I am attempting to build a 90mm 2s quad, however it is proving to be more difficult than anticipated! Anyway, I digress. The issue I am facing is such: I have bound my RX (FrSky Ultralight XM Receiver) to my TX (Taranis Q X7) and soldered (correctly this time) it to my FC board (Super_S F3) but when I go into BetaFlight to check the receiver, nothing changes with inputs from the TX. The RX shows, with the little green light, that it is connected to the TX, so I don't believe that to be the issue, so I am lost! I am encountering a second issue, but I don't know if it related to the first. I am able to connect the FC to BetaFlight, however when I try to flash a newer version of OmniBus to the FC, the serial port consistently fails to open. Any advice would be very much appreciated!

Here is a list of parts for the build, if needed:

FC and ESCs - USAQ Betaflight F3 Micro 6A 2S 4-In-1 Brushless ESC OSD Flight Controller Micro Cube

RX - FrSky Ultralight XM Receiver (I also have a FrSky XSR receiver, though that might be a bit big for the build)

Motors - Crazypony D1103 10000Kv Brushless Motors

Battery - 350mAh 2s (I can't seem to find the brand)

FPV Camera/VTX - Boldclash F-02 FPV AIO Camera

Props - Gemfan 2040 Triblade Propellers 2.0 Inch
 

ElectriSean

Eternal Student
Mentor
#2
Your flashing problems are probably driver related, did you do the Zadig driver install?

As to the Rx/FC issue, can you post some pictures of your connections, as well as screenshots from the receiver and configuration tabs from Betaflight?
 
#4
Unfortunately there seems to be a technical issue when attaching the pictures to the thread so I will try to find a different way to upload them. When taking the pictures I noticed that the receiver mode was set to PPM, so I tried to change that, but when I hit save and reboot, the serial port failed to close, so I am reinstalling all of the drivers. Hopefully that will help.
Edit:
Here is the link to the pictures:
https://photos.app.goo.gl/Lgc6OZiagsHvJKqf1

Also, the reinstallation of the drivers has not solved the problem, so I am again stuck.
 
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TazRC

Obsession, not hobby
#5
I don't know that specific FC but did you try using a manual baud rate, like 115200, for Betaflight connection?
 

ElectriSean

Eternal Student
Mentor
#6
Many people have had success using the ImpulseRC driver fixer available here: https://impulserc.com/pages/downloads

There are 3 main settings in BF to get your Rx communicating. First, in the ports tab you have to enable serial_rx on whatever UART you soldered your SBUS wire to. If the pad on the FC is just labelled SBUS you'll have to check the documentation that came with the FC to find out which port it is. Second, in the configuration tab you have to set the receiver type to Serial. Finally, the serial provider has to be set to SBUS. Make sure you hit the save and reboot button before changing tabs or your settings will be lost.
 

Snarls

Gravity Tester
Mentor
#7
The ImpulseRC driver fix tool has saved me much a headache when dealing with driver problems. Definitely a tool worth keeping around.
 

Bricks

Well-known member
#8
Depending on what SBUS you soldered to if it is the same as the USSB port for flashing firmware it will not work unless you unsolder it.
 
#9
Aha! We have solved the problem! Well, sort of... I got everything to connect and all of the channels to go the correct direction (all but one, as I found out), then took off, and promptly flew into a door because that last channel was backwards. Ripped a few crucial pads off the FC, so this one is gone for now. Use my Christmas money to buy a new frame and FC so I will try again and this time be more careful (lower rates are more expo might also help)! Thank you all for your help, it is much appreciated! When I get the next version flying I will try to put a video up on the forum. Thanks again for all your wonderfully helpful input!
-(WhittyFlightJokeHere)
 
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#10
I am having a similar problem with my quad too regarding a flight controller not responding to my spektrum racing serial reciever. The flight controller is a holybro kakute f4 v.14, running betaflight. I have the three reciever wires soldered to the 3.3v, ground, and the UART3 pad. When I plug in my 4s into the drone, the reciever lights up and goes into bind mode. I am able to successfully bind to the drone, yet it doesn't respond to any inputs, even when I plug it into betaflight. I am new to Betaflight, and am familiar with librepilot. Furthermore, I am pretty new to drones as well, but have been in the hobby flying rc planes for years. The drone is the furibee x215 pro plug and play. Any input, or suggestions would be greatly appreciated. Thank you Betaflight, and am familiar with librepilot. Furthermore, I am pretty new to drones as well, but have been in the hobby flying rc planes for years. The drone is the furibee x215 pro plug and play. Any input, or suggestions would be greatly appreciated. Thank you
 

ElectriSean

Eternal Student
Mentor
#11
I am having a similar problem with my quad too regarding a flight controller not responding to my spektrum racing serial reciever. The flight controller is a holybro kakute f4 v.14, running betaflight. I have the three reciever wires soldered to the 3.3v, ground, and the UART3 pad. When I plug in my 4s into the drone, the reciever lights up and goes into bind mode. I am able to successfully bind to the drone, yet it doesn't respond to any inputs, even when I plug it into betaflight. I am new to Betaflight, and am familiar with librepilot. Furthermore, I am pretty new to drones as well, but have been in the hobby flying rc planes for years. The drone is the furibee x215 pro plug and play. Any input, or suggestions would be greatly appreciated. Thank you Betaflight, and am familiar with librepilot. Furthermore, I am pretty new to drones as well, but have been in the hobby flying rc planes for years. The drone is the furibee x215 pro plug and play. Any input, or suggestions would be greatly appreciated. Thank you
In the ports tab, enable Serial_rx on UART3, save and reboot. Then in the configuration tab, set receiver type to Serial, and serial provider to SPEKTRUM2048.
 
#12
Ok, I got betaflight to respond to my transmitter inputs yet cannot get the drone to arm. I went into the modes tab and set the arming settings to aux 1. When I flip the switch on my transmitter, the drone will beep, and the flight controller will flash blue, but nothing will happen when I give it throttle input. Any suggestions would be great