Imagine a drone flying steadily through the air, executing each command with precision. Behind this seamless operation lies the coordinated work of electronic speed controllers (ESCs) and motors, translating flight controller instructions into actual power output. The selection and configuration of ESC protocols play a crucial role in achieving optimal drone performance.

In PX4 drone systems, brushless motors serve as the vital propulsion components. These motors are driven by electronic speed controllers (ESCs) that receive signals from the flight controller. The ESC interprets these commands to regulate power delivery to the motor, enabling precise control over rotational speed.

The PX4 flight control system supports multiple ESC communication protocols, each with distinct advantages and ideal use cases:

Pulse Width Modulation (PWM) represents a traditional protocol that adjusts motor power by varying pulse duration. While commonly used in fixed-wing aircraft and ground vehicles where latency isn't critical, most multirotor applications favor faster alternatives like OneShot or DShot due to their superior response times.

OneShot protocols offer significantly faster response than PWM, making them preferable for multirotor aircraft. Among its variants, PX4 currently supports only OneShot 125. While outperforming PWM, OneShot has been largely superseded by DShot in modern applications.

This digital protocol delivers low latency, exceptional reliability, and strong interference resistance. DShot proves ideal for response-sensitive applications like racing drones and VTOL aircraft. Additional benefits include elimination of calibration requirements and optional telemetry feedback support in certain models.

Recommended for systems utilizing DroneCAN bus as primary communication, this protocol offers high data rates, stable connections, telemetry feedback, and no calibration needs. Current PX4 implementations cap the update rate at 200Hz.

The system also supports PCA9685 ESCs (via I2C bus) and certain UART ESCs from Yuneec.

PWM ESCs control motors through periodic pulses, where width determines power level. Standard ranges use 1000μs for zero power and 2000μs for full power. Frame rates typically span 50-490Hz, with theoretical maximums near 500Hz. Higher rates benefit ESC performance, particularly when rapid response to setpoint changes is required.

Limitations include:

• Relatively slow response times
• Mandatory calibration due to variance in high/low value ranges across ESCs
• Lack of telemetry feedback capabilities

This protocol reduces pulse widths by 8x compared to PWM (125-250μs range), enabling shorter duty cycles and higher refresh rates. While PWM maxes near 500Hz, OneShot theoretically approaches 4kHz, though actual performance depends on specific ESC capabilities.

This digital protocol significantly reduces latency while improving robustness. Configuration eliminates calibration requirements and allows motor rotation reversal. DShot offers multiple speed options (150, 300, 600, 1200) where higher rates decrease latency but lower rates enhance stability—particularly beneficial for larger aircraft with extended wiring.

Sharing many DShot advantages, DroneCAN excels in high-data-rate applications with robust long-distance connections. The 200Hz update rate limitation remains its primary constraint in PX4 implementations.

Choosing the appropriate protocol depends on specific application requirements:

• Fixed-wing/ground vehicles: PWM often suffices
• Multirotor aircraft: OneShot 125 or DShot (preferred for racing drones)
• DroneCAN-based systems: DroneCAN ESCs provide optimal integration

PWM and OneShot ESCs require calibration to ensure proper response to control signals. This process involves setting minimum and maximum throttle values. DShot and DroneCAN implementations eliminate this requirement.

Selecting and properly configuring ESC protocols fundamentally impacts drone performance. Understanding the technical characteristics and operational requirements enables builders to create more efficient, reliable unmanned systems. This examination of PX4's ESC protocol options provides a foundation for informed decision-making in drone development projects.