# DroneCAN ESCs

PX4 supports DroneCAN compliant ESCs.

## Supported ESC

:::info
[Supported ESCs](../peripherals/esc_motors.md#supported-esc) in _ESCs & Motors_ may include additional devices that are not listed below.
:::

The following articles have specific hardware/firmware information:

- [PX4 Sapog ESC Firmware](sapog.md)
  - [Holybro Kotleta 20](holybro_kotleta.md)
- [Zubax Telega](zubax_telega.md)
- [Vertiq](../peripherals/vertiq.md) (larger modules)
- [VESC Project](../peripherals/vesc.md)
- [RaccoonLab Cyphal and DroneCAN PWM nodes](raccoonlab_nodes.md)

## 硬件配置

General DroneCAN hardware configuration is covered in [DroneCAN > Hardware Setup](../dronecan/index.md#hardware-setup).

DroneCAN ESCs should be on their own dedicated CAN interface(s) because ESC messages can saturate the bus and starve other nodes of bandwidth.

## PX4 配置

DroneCAN peripherals are configured by following the procedure outlined in [DroneCAN](../dronecan/index.md).

In addition to the general setup:

- Set [UAVCAN_ENABLE](../advanced_config/parameter_reference.md#UAVCAN_ENABLE) to `3`.

::: tip TIP
<Badge type="tip" text="main (PX4 v2.0)" />
  There is no need to enable [UAVCAN_PUB_ARM](../advanced_config/parameter_reference.md#UAVCAN_PUB_ARM).

  In earlier versions you would need to set `UAVCAN_PUB_ARM=1` in order to publish the [ArmingStatus](https://dronecan.github.io/Specification/7._List_of_standard_data_types/#armingstatus) (this is required by some ESCs in order to respond correctly during both flight and Actuators page tests).
  The status is now published automatically if `UAVCAN_ENABLE=3`.

:::

- Select the specific CAN interface(s) used for ESC data output using the [UAVCAN_ESC_IFACE](../advanced_config/parameter_reference.md#UAVCAN_ESC_IFACE) parameter (all interfaces are selected by default).

- Configure the [motor order and servo outputs](../config/actuators.md).

## Known Quirks {#known-quirks}

Sadly some DroneCAN devices deviate from the DSDL specification in ways that require a workaround on the PX4 side.
These workarounds are disabled by default and can be enabled with the [UAVCAN_QUIRKS](../advanced_config/parameter_reference.md#UAVCAN_QUIRKS) bitmask parameter.

- **Hobbywing ESCs:** some Hobbywing DroneCAN ESCs report `uavcan.equipment.esc.Status.esc_index` starting at 1 for the first ESC instead of 0 as required by the specification, while still expecting `RawCommand.cmd[0]` to command the first ESC.
  This causes ESC status feedback (e.g. RPM, voltage, current) to be matched to the wrong motor.
  Set bit 0 of `UAVCAN_QUIRKS` to correct for this off-by-one indexing.

## Reversible Motors {#reversible-motors}

<Badge type="tip" text="main (PX4 v2.0)" />

Motors can be reversible "on the fly" (bidirectional) if the motor hardware supports reversal, the ESC firmware is configured for 3D/bidirectional operation, and the motor is set as [bidirectional](../config/actuators.md#bidirectional-motors) in the actuator configuration.

When configured as bidirectional, PX4 commands the motor with a _signed_ `uavcan.equipment.esc.RawCommand` value, as defined by the DroneCAN ESC message protocol:

- **Zero:** Motor stop / neutral
- **Positive values:** Forward thrust
- **Negative values:** Reverse thrust

Motors that are not configured as bidirectional continue to receive positive values only.

:::tip
Verifying Operation
Check the sign of the RPM reported in the ESC telemetry to confirm that the ESC is interpreting negative commands correctly and actively spinning the motor in reverse.
:::

Reversible motors may also be used in [Motor Failure Recovery](../config/motor_failure_recovery.md) to keep a hexarotor controllable after a single motor failure.
That case still needs ESCs configured for reversal.
However it is not necessary to set the motor as bidirectional in the actuator configuration, because PX4 makes the recovery motor reversible as it handles the failure.