Dear Fan007,
on the RDDRONE-BMS772 there are populated three shunt temperature resistors. RT1, RT2 and RT3.
RT1 and RT2 are located on top of the board.

The RT3 is located on the bottom of the board, below the MC33772B, to measure it's temperature.

Please check the schematic attached, how the RT1 through RT3 are routed. RT1 is routed to the GPIO0, RT2 to the GPIO2 and RT3 to GPIO3. You can use the GPIO1 pin to measure temperature. You need to connect a 10k shunt resistor on the J1 connector. The GPIO4 has already different function. Therefore GPIO4 cannot be use for temperature measurement on the RDDRONE-BMS772. The GPIO5 and GPIO6 are not connected. They cannot be used. Please use the four GPIO pins for temperature measurement.
With Best Regards,
Jozef