Flysky FS-X6B firmware update using openocd, successfully.

[kindsoldier]

I share my experience.
Flashing the receiver is like flashing typical stm32f* but I am faced with the fact that memory bank of the receiver is locked for write at factory.
Unlock sequence:

# openocd \
     -f interface/stlink-v2.cfg \
     -f target/stm32f0x.cfg \
     -c "init" \
     -c "reset halt" \
     -c "stm32f0x unlock 0" \
     -c "reset halt" \
     -c "shutdown"

After that it is flashed with a typical sequence of openocd commands:

 # image=X6B_rssi_ch14.bin
 # openocd \
    -f 'interface/stlink-v2.cfg' \
    -f 'target/stm32f0x.cfg'  \
    -c "init" \
    -c "reset halt" \
    -c "flash write_image erase $image 0x08000000"\
    -c "verify_image $image" \
    -c "reset" \
    -c "shutdown"

I use clone STLink V2 from Aliexpress.
Important! Also I soldered and connect to STLink "Reset" line on the receiver.

After that I got RSSI on channel 14 (Aux10)

For save original firmware:
# st-flash read ./firmware-orig.bin 0x08000000 0x8000

No guarantees, of course. =)

PS

I found that you can unlock flash memory immediately when recording. http://openocd.org/doc/html/Flash-Commands.html

Command: flash write_image [erase] [unlock] filename [offset] [type]

That should work.