Before trying the following steps, please firstly refer to this video:
If still in vain, please try:
1. First of all, check the connection and setting by referring to
2. Make sure the firmware version of your flight controller is up to date.
- BetaFlight version 3.2.0 or above
- CleanFlight version 2.1.0 or above
3. Tx, Rx, GND should be well connected to a UART's Rx, Tx, GND of your Flight Controller:
4. Make sure your transmitter(Tx) is bounded well with the receiver(Rx). In other words, you can arm/disarm your quad.