1. Anonymous host computer PID tuning2. Complementary filtering attitude solution, cascade PID3. NRF24L01 2.4G remote control, OLED real-time display four-axis attitude, voltage return, can be secondary development4. STM32F103 master control, integrated MPU6050, BMP280 barometer, WS2812B full-color indicator light, reserved expandable interface2. Supporting remote control: https://www.pcbway.com/project/shareproject/Open_source_four_axis_remote_control_1.html1. The motor is 8520 hollow cup motor, and the power supply is 3.7V 1S lithium battery2. Lead out the SWD program burning interface, need an emulator [ST-LINK is cheaper]4. The diameter of the mounting hole of the hollow cup is 8.52mm. The mounting hole is larger than the motor diameter. You need to 3D print the motor base. You can also change the mounting hole to a smaller point: 8.50 ~ 8.52mm [8.50mm is particularly tight. , Need polishing]