An advanced, compact 4-axis flight controller built entirely around the ESP32 microcontroller. This project features a custom-designed 4-layer printed circuit board (PCB), real-time PID stabilization, I-Bus radio protocol decoding, and live telemetry/tuning over Bluetooth.
- Custom 4-Layer PCB: Designed with dedicated Ground (GND), Power, and two data routing layers to optimize space and minimize signal interference.
- 6-Axis Inertial Navigation: Utilizes the MPU6050 IMU to calculate high-precision tilt angles (Pitch/Roll) and angular velocity via its internal Digital Motion Processor (DMP).
- Real-Time Bluetooth Tuning: Dynamically adjust PID coefficients and request battery voltage monitoring on-the-fly using a Bluetooth terminal application.
- I-Bus Protocol Receiver Integration: Decodes multichannel inputs from a FLY-SKY FS-i6X radio transmitter natively over hardware UART.
- Robust Hardware Safety Suite: Features an angle-based emergency cutoff mechanism (kills motors if tilt exceeds 45°) and a dedicated switch-arm safety sequence.
- Integrated Battery Monitoring: Employs an onboard resistor voltage divider for real-time low-voltage detection.
- Microcontroller: ESP32-WROOM-32D-N16
- IMU Sensor: MPU6050 Module
- RC Receiver: FLY-SKY FS-i6X (I-Bus compatible)
- Actuators: 4x Brushless DC Motors with Electronic Speed Controllers (ESCs)
- Power Supply: 4S Li-Po Battery (1550 mAh) stepped down via a DC-DC buck converter
| Peripheral Component | ESP32 Pin | Function Description |
|---|---|---|
| ESC Left-Front (LF) | IO18 | PWM Motor Control Output |
| ESC Left-Rear (LR) | IO0 | PWM Motor Control Output |
| ESC Right-Front (RF) | IO5 | PWM Motor Control Output |
| ESC Right-Rear (RR) | IO4 | PWM Motor Control Output |
| I-Bus RX Pin | IO16 | Hardware Serial UART2 Input |
| MPU6050 Interrupt | IO2 | IMU Data Ready Trigger |
| Voltage Divider Sense | IO34 | Analog Battery Telemetry Input |
| Status LED | IO12 | Visual Indicator |
The software relies on high-speed sampling of the IMU's raw angular metrics combined with pilot stick mapping to dictate corrective motor speeds via localized mixing equations.
LF = boolKill * (T * throttle + 0.1 * P * (ROLL + Rstick * S) + 0.1 * P * (PITCH - Pstick * S) + 0.001 * D * gy + 0.001 * D * gx + I * I_PITCH + I * I_ROLL + Y * Ystick);
LR = boolKill * (T * throttle + 0.1 * P * (ROLL + Rstick * S) - 0.1 * P * (PITCH - Pstick * S) + 0.001 * D * gy - 0.001 * D * gx - I * I_PITCH + I * I_ROLL - Y * Ystick);
RF = boolKill * (T * throttle - 0.1 * P * (ROLL + Rstick * S) + 0.1 * P * (PITCH - Pstick * S) - 0.001 * D * gy + 0.001 * D * gx + I * I_PITCH - I * I_ROLL - Y * Ystick);
RR = boolKill * (T * throttle - 0.1 * P * (ROLL + Rstick * S) - 0.1 * P * (PITCH - Pstick * S) - 0.001 * D * gy - 0.001 * D * gx - I * I_PITCH - I * I_ROLL + Y * Ystick);By pairing with the system via Bluetooth (ProjectX), you can pass live terminal strings configured as [Command]|[Value]\n to tweak handling metrics or review vital diagnostics:
P|[value]- Set Proportional GainI|[value]- Set Integral GainD|[value]- Set Derivative GainT|[value]- Set Throttle ScaleB- Echoes real-time 4S battery voltage metrics
Below is a render of the compact routing layout engineered specifically for this flight controller:
Here is the completed, fully assembled quadcopter hardware in its final form, utilizing the custom-designed 4-layer flight controller PCB and ESP32 core stabilization system[cite: 2, 3].
