Jumper R9 Mini
Jumper RX R900MINI
Wire it up to your STLink V2 as follows:
+ = 3v3,
- = GND,
C = CLK and
D = DIO to their respective pins on the RX from the StLink.
Because those pins are so small one option is to only solder a wire on the
DIO then power it with the 5v pin with an external power source.
Using the correct target specific for your receiver, and your Firmware Options set, click Build & Flash on the ExpressLRS Configurator.
After the flash is successful, desolder the STLink and connect RX2 and TX2 (you will need to solder on the STM32 pins, see picture) to a flight controller and setting up the receiver with the CRSF serial protocol, the
Jumper_RX_R900MINI_via_BetaflightPassthrough target may now be used for future firmware updates.