mirror of
https://gitee.com/mirrors_PX4/PX4-Autopilot.git
synced 2026-05-16 20:07:35 +08:00
Jacob Dahl
f00e46f618
Overhauls the DShot driver with per-timer BDShot selection, multi-timer
sequential capture, Extended DShot Telemetry (EDT), and AM32 ESC EEPROM
read/write via MAVLink. Expands ESC support from 8 to 12 channels.
BDShot:
- Per-timer BDShot protocol selection via actuator config UI
- Multi-timer sequential burst/capture on any DMA-capable timer
- Adaptive per-channel GCR bitstream decoding
- Per-channel online/offline detection with hysteresis
Extended DShot Telemetry (EDT):
- Temperature, voltage, current from BDShot frames (no serial wire)
- New DSHOT_BIDIR_EDT parameter
- EDT data merged with serial telemetry when both available
AM32 EEPROM:
- Read/write AM32 ESC settings via MAVLink ESC_EEPROM message
- ESCSettingsInterface abstraction for future ESC firmware types
- New DSHOT_ESC_TYPE parameter
Other changes:
- Per-motor pole count params DSHOT_MOT_POL1–12 (replaces MOT_POLE_COUNT)
- EscStatus/EscReport expanded to 12 ESCs with uint16 bitmasks
- Numerous bounds-check, overflow, and concurrency fixes
- Updated DShot documentation
147 lines
7.1 KiB
Markdown
147 lines
7.1 KiB
Markdown
# DShot ESCs
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DShot is an alternative ESC protocol that has several advantages over [PWM](../peripherals/pwm_escs_and_servo.md) or [OneShot](../peripherals/oneshot.md):
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- Reduced latency.
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- Increased robustness via a checksum.
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- No need for ESC calibration as the protocol uses digital encoding.
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- Telemetry feedback is available/supported on some ESCs.
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- Can reverse motor spin directions via commands when needed (rather than physically moving wires/re-soldering).
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- Other useful commands are supported.
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This topic shows how to connect and configure DShot ESCs.
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## Supported ESC
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[ESCs & Motors > Supported ESCs](../peripherals/esc_motors#supported-esc) has a list of supported ESC (check "Protocols" column for DShot ESC).
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## Wiring/Connections {#wiring}
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DShot ESC are wired the same way as [PWM ESCs](pwm_escs_and_servo.md).
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The only difference is that they can only be connected to the FMU, and usually only to some subset of pins.
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::: info
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You may want to check the actuator configuration screen to see what pins are available for DShot on your controller before wiring up!
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:::
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Pixhawk controllers with both an FMU and an IO board usually label them as `AUX` (FMU) and `MAIN` (IO), respectively.
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These match the `PWM AUX` and `PWM MAIN` output tabs on the actuator configuration screen.
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For these controllers connect the DShot ESC to the `AUX` port.
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Controllers that don't have an IO board usually label the (single) output port as `MAIN`, and this is where you will connect your DShot ESC.
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If the controller without IO has its own firmware, the actuator assignment will be to the matching `PWM MAIN` outputs.
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However if the same firmware is used for hardware with/without the IO board, such as for the Pixhawk 4 and Pixhawk 4 Mini, then actuator assignment tab used is the same in both cases: `PWM AUX` (i.e. not matching the port label `MAIN` in the "mini" case).
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## Configuration
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:::warning
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Remove propellers before changing ESC configuration parameters!
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:::
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Enable DShot for your required outputs in the [Actuator Configuration](../config/actuators.md).
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DShot comes with different speed options: _DShot150_, _DShot300_, and _DShot600_ where the number indicates the speed in kilo-bits/second.
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You should set the parameter to the highest speed supported by your ESC (according to its datasheet).
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Then connect the battery and arm the vehicle.
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The ESCs should initialize and the motors turn in the correct directions.
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- If the motors do not spin in the correct direction (for the [selected airframe](../airframes/airframe_reference.md)) you can reverse them in the UI using the **Set Spin Direction** option (this option appears after you select DShot and assign motors).
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## ESC Commands {#commands}
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Commands can be sent to the ESC via the [MAVLink shell](../debug/mavlink_shell.md).
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See [here](../modules/modules_driver.md#dshot) for a full reference of the supported commands.
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## ESC Telemetry
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Some ESCs are capable of sending telemetry back to the flight controller through a UART RX port.
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These DShot ESCs will have an additional telemetry wire.
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The provided telemetry includes:
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- Temperature
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- Voltage
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- Current
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- Accumulated current consumption
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- RPM values
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To enable this feature (on ESCs that support it):
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1. Join all the telemetry wires from all the ESCs together, and then connect them to one of the RX pins on an unused flight controller serial port.
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2. Enable telemetry on that serial port using [DSHOT_TEL_CFG](../advanced_config/parameter_reference.md#DSHOT_TEL_CFG).
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:::tip
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You may have to configure the per-motor pole count parameters ([`DSHOT_MOT_POL1`–`DSHOT_MOT_POL12`](../advanced_config/parameter_reference.md#DSHOT_MOT_POL1)) to get correct RPM values.
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The default value for these is 14 poles, which is typical for 5-inch prop motors.
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:::
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:::tip
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[Extended DShot Telemetry (EDT)](#extended-dshot-telemetry-edt) can provide temperature, voltage, and current through the BDShot signal — no serial telemetry wire needed.
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:::
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## Bidirectional DShot (Telemetry)
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<Badge type="tip" text="PX4 v1.16" />
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Bidirectional DShot (BDShot) enables the ESC to send eRPM telemetry back to the flight controller on the same signal wire used for throttle commands — no additional telemetry wire is needed for RPM data.
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High-rate eRPM data significantly improves the performance of [Dynamic Notch Filters](../config_mc/filter_tuning.md#dynamic-notch-filters) and enables more precise vehicle tuning.
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With [Extended DShot Telemetry (EDT)](#extended-dshot-telemetry-edt) enabled, BDShot can also provide temperature, voltage, and current data.
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### Hardware Support
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BDShot requires a flight controller with DMA-capable timers.
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Any FMU output on a supported timer can be used for BDShot — multiple timers are supported through sequential burst/capture.
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Supported processors:
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- **STM32H7**: All FMU outputs on DMA-capable timers
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- **i.MXRT** (V6X-RT & Tropic): All FMU outputs
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::: info
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The ESC must be connected to FMU outputs only.
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These are labeled `MAIN` on controllers with a single PWM bus, and `AUX` on controllers with both `MAIN` and `AUX` ports (i.e. those with an IO board).
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:::
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### PX4 Configuration {#bidirectional-dshot-configuration}
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BDShot is enabled **per-timer** in the [Actuator Configuration](../config/actuators.md) UI.
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Select **BDShot150**, **BDShot300**, or **BDShot600** as the output protocol instead of the corresponding DShot speed.
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There is no separate enable parameter — choosing a BDShot protocol activates bidirectional telemetry on that timer's outputs.
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The system calculates actual motor RPM from eRPM data using per-motor pole count parameters: `DSHOT_MOT_POL1` through `DSHOT_MOT_POL12` (one per motor output).
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The default is 14 poles, which is typical for 5-inch prop motors.
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If you are using AM32 ESCs, the motor pole count must also be set in the AM32 firmware configuration (e.g. via the AM32 configurator tool) to match.
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### Extended DShot Telemetry (EDT)
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EDT extends BDShot by interleaving temperature, voltage, and current data into the eRPM telemetry frames.
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This allows ESC health monitoring through the same signal wire, without requiring a separate serial telemetry connection.
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To enable EDT:
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1. Configure BDShot on the desired outputs (see above).
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2. Set `DSHOT_BIDIR_EDT` to `1` and reboot.
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The ESC firmware must support EDT (e.g. [AM32](https://github.com/am32-firmware/AM32)).
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When both serial telemetry and BDShot/EDT are enabled, the driver merges data from both sources.
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## AM32 ESC Settings (EEPROM)
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PX4 can read and write AM32 ESC firmware settings (EEPROM) via a ground station, enabling remote ESC configuration without connecting directly to each ESC.
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### Requirements
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- ESCs running [AM32 firmware](https://github.com/am32-firmware/AM32) with serial telemetry connected ([DSHOT_TEL_CFG](../advanced_config/parameter_reference.md#DSHOT_TEL_CFG))
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- `DSHOT_ESC_TYPE` set to `1` (AM32)
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- Ground station with ESC EEPROM support (QGroundControl feature in development)
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- MAVLink development dialect enabled on the flight controller
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### How It Works
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PX4 automatically reads the full EEPROM from each ESC on boot.
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The ground station can then display individual settings and allow the user to modify them.
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Changes are written back to the ESC one byte at a time using the DShot programming protocol.
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