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67 lines
3.9 KiB
Markdown
67 lines
3.9 KiB
Markdown
# ESC Protocols
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This topic lists the main [Electronic Speed Controller (ESC)](../peripherals/esc_motors.md) protocols supported by PX4.
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## DShot
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[DShot](../peripherals/dshot.md) is a digital ESC protocol that is highly recommended for vehicles that can benefit from reduced latency, in particular racing multicopters, VTOL vehicles, and so on.
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It has reduced latency and is more robust than both [PWM](#pwm) and [OneShot](#oneshot-125).
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In addition it does not require ESC calibration, telemetry is available from some ESCs, and you can reverse motor spin directions.
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PX4 configuration is done in the [Actuator Configuration](../config/actuators.md).
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Selecting a higher rate DShot ESC in the UI results in lower latency, but lower rates are more robust (and hence more suitable for large aircraft with longer leads); some ESCs only support lower rates (see datasheets for information).
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Setup:
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- [ESC Wiring](../peripherals/pwm_escs_and_servo.md) (same as for PWM ESCs)
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- [DShot](../peripherals/dshot.md) also contains information about how to send commands etc.
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## DroneCAN
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[DroneCAN ESCs](../dronecan/escs.md) are recommended when DroneCAN is the primary bus used for your vehicle.
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The PX4 implementation is currently limited to update rates of 200 Hz.
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DroneCAN shares many similar benefits to [DShot](#dshot) including high data rates, robust connection over long leads, telemetry feedback, no need for calibration of the ESC itself.
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[DroneCAN ESCs](../dronecan/escs.md) are connected via the DroneCAN bus (setup and configuration are covered at that link).
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## PWM
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[PWM ESCs](../peripherals/pwm_escs_and_servo.md) are commonly used for fixed-wing vehicles and ground vehicles (vehicles that require a lower latency like multicopters typically use oneshot or dshot ESCs).
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PWM ESCs communicate using a periodic pulse, where the _width_ of the pulse indicates the desired speed.
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The pulse width typically ranges between 1000 μs for zero power and 2000 μs for full power.
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The periodic frame rate of the signal depends on the capability of the ESC, and commonly ranges between 50 Hz and 490 Hz (the theoretical maximum being 500 Hz for a very small "off" cycle).
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A higher rate is better for ESCs, in particular where a rapid response to setpoint changes is needed.
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For PWM servos 50 Hz is usually sufficient, and many don't support higher rates.
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In addition to being a relatively slow protocol PWM ESCs require [calibration](../advanced_config/esc_calibration.md) because the pulse widths representing low and high values can vary significantly.
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Unlike [DShot](#dshot) and [DroneCAN ESC](#dronecan) they do not have the ability to provide telemetry and feedback on ESC (or servo) state.
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Setup:
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- [ESC Wiring](../peripherals/pwm_escs_and_servo.md)
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- [PX4 Configuration](../peripherals/pwm_escs_and_servo.md#px4-configuration)
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- [ESC Calibration](../advanced_config/esc_calibration.md)
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## OneShot 125
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[OneShot 125 ESCs](../peripherals/oneshot.md) are usually much faster than PWM ESCs, and hence more responsive and easier to tune.
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They are preferred over PWM for multicopters (but not as much as [DShot ESCs](#dshot), which do not require calibration, and may provide telemetry feedback).
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There are a number of variants of the OneShot protocol, which support different rates.
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PX4 only supports OneShot 125.
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OneShot 125 is the same as PWM but uses pulse widths that are 8 times shorter (from 125 μs to 250 μs for zero to full power).
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This allows OneShot 125 ESCs to have a much shorter duty cycle/higher rate.
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For PWM the theoretical maximum is close to 500 Hz while for OneShot it approaches 4 kHz.
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The actual supported rate depends on the ESC used.
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Setup:
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- [ESC Wiring](../peripherals/pwm_escs_and_servo.md) (same as for PWM ESCs)
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- [PX4 Configuration](../peripherals/oneshot.md#px4-configuration)
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- [ESC Calibration](../advanced_config/esc_calibration.md)
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