> ## Documentation Index
> Fetch the complete documentation index at: https://docs.intrusiverobotics.com/llms.txt
> Use this file to discover all available pages before exploring further.
# UAVCAN / DroneCAN
> Run the Delta GaN ESC as a UAVCAN v0 (DroneCAN) node with PX4 or ArduPilot — CAN mode, node ID, ESC index, raw command modes, and telemetry.
The Delta can act as a **UAVCAN ESC node**, taking throttle commands from a flight controller over CAN instead of PPM, ADC, or UART.
**Works with both PX4 and ArduPilot.** The Delta implements UAVCAN v0 (DroneCAN) — the CAN ESC protocol both autopilots use. Either one can command the Delta and read its telemetry over the bus.
**This is UAVCAN v0, now called DroneCAN.** It is *not* UAVCAN v1 / Cyphal.
The two are different, incompatible protocols that share a name. The Delta firmware implements v0 via `libcanard`. **Both PX4 and ArduPilot use v0**, so this is the correct and compatible protocol for either — it is what they mean when their ESC configuration says "DroneCAN" or "UAVCAN".
## Enabling UAVCAN mode
In VESC Tool, under **App Settings → General → CAN**, set **CAN Mode** to `UAVCAN`.
| CAN Mode | Behaviour |
| ------------- | ---------------------------------------------------------------------------------- |
| `VESC` | Default. VESC-native CAN — multi-controller setups, CAN forwarding from VESC Tool. |
| `UAVCAN` | The controller becomes a UAVCAN ESC node and takes commands from the bus. |
| `Comm Bridge` | Bridges the CAN bus to the serial link. |
Switching to `UAVCAN` changes what the CAN bus is used for. VESC-native CAN behaviour — including CAN forwarding, which is how VESC Tool reaches a second controller over the bus — no longer applies in the same way. Configure each controller over USB before putting it on a UAVCAN bus.
## Core settings
| Setting | Range | Default | What it does |
| ------------------------------ | ------------- | ------- | ------------------------------------------------------------ |
| **CAN Baud Rate** | 10K – 1M | 500K | Must match every other node on the bus. |
| **Controller ID** | 0 – 253 | 0 | The **UAVCAN node ID**. Must be unique on the bus. |
| **UAVCAN ESC Index** | 0 – 255 | 0 | Which slot of the command array this controller responds to. |
| **UAVCAN Raw Mode** | see below | Current | How `RawCommand` is interpreted. |
| **UAVCAN Raw RPM Max** | — | — | Full-scale RPM, used only in RPM raw mode. |
| **UAVCAN Status Current Mode** | Motor / Input | Motor | Which current is reported in ESC status. |
**Node ID and ESC index are different things.** The node ID identifies the controller on the bus. The ESC index selects which element of the throttle array it obeys.
On a multi-motor vehicle each controller needs **both** a unique node ID and the ESC index matching its motor position in the flight controller's motor ordering.
## Raw command modes
The flight controller broadcasts `uavcan.equipment.esc.RawCommand` — an array of setpoints, one per ESC. The Delta reads the element at its configured ESC index and scales it by 8192, giving a value from **−1.0 to 1.0**.
What it does with that value depends on the raw mode:
| Raw mode | Behaviour |
| ----------------------------- | --------------------------------------------------------------------------------------------------------------------------- |
| **Current** | Sets relative motor current across the full range. Negative values drive the motor in reverse. |
| **Current, no reverse brake** | Positive sets relative current; negative applies **braking** current instead of reversing. The usual choice for propellers. |
| **Duty** | Sets duty cycle directly. |
| **RPM** | Closed-loop speed control at `value x UAVCAN Raw RPM Max`. Requires Raw RPM Max to be set. |
On a propeller-driven aircraft, **Current** mode will spin the motor backwards on a negative command. Use **Current, no reverse brake** unless you specifically want reversing.
The Delta also accepts `uavcan.equipment.esc.RPMCommand`, which takes the RPM value at its ESC index directly rather than as a scaled fraction.
## Telemetry
The Delta publishes `uavcan.equipment.esc.Status`, tagged with its configured ESC index.
**UAVCAN Status Current Mode** selects which current appears in that message:
* **Motor** — current through the motor phases
* **Input** — current drawn from the battery
Pick to match what your flight controller expects, otherwise logged current will be consistently wrong.
Status broadcast rates are configurable through the UAVCAN parameter service (`can_status_rate_1`, default 50; `can_status_rate_2`, default 5).
## Supported UAVCAN interfaces
| Interface | Direction |
| --------------------------------- | ---------- |
| `uavcan.equipment.esc.RawCommand` | Subscribed |
| `uavcan.equipment.esc.RPMCommand` | Subscribed |
| `uavcan.equipment.esc.Status` | Published |
| `uavcan.protocol.NodeStatus` | Published |
| `uavcan.protocol.GetNodeInfo` | Served |
| `uavcan.protocol.param.GetSet` | Served |
| `uavcan.protocol.RestartNode` | Served |
Firmware update over UAVCAN is also implemented.
### Parameters exposed over the bus
These can be read and written with any UAVCAN parameter tool, without connecting VESC Tool:
| Parameter | Range | Default |
| -------------------- | -------- | ------- |
| `controller_id` | 0 – 253 | 0 |
| `can_esc_index` | 0 – 255 | 0 |
| `can_baud_rate` | 0 – 8 | 500K |
| `can_status_rate_1` | 0 – 1000 | 50 |
| `can_status_rate_2` | 0 – 1000 | 5 |
| `can_status_msgs_r1` | 0 – 255 | 0 |
| `can_status_msgs_r2` | 0 – 255 | 0 |
| `ctl_dir` | 0 – 1 | 0 |
## Bringing up a bus
Props off. A wrong ESC index means the wrong motor spins, and you want to discover that on the bench.
Set CAN Mode to `UAVCAN`, assign a unique Controller ID, set the ESC index for that motor position, and pick the raw mode. Write and verify before moving to the next controller.
Every node on the bus must agree. 500K is the default and the usual choice.
CAN H, CAN L, and a common ground — **leave the Delta's 3.3 V pin unconnected**. Termination matters: a UAVCAN bus needs 120 Ω at each physical end.
Each controller should appear in your flight controller's UAVCAN node list with the node ID you assigned. A missing node is a wiring, baud, or duplicate-ID problem.
Command each motor position individually and confirm the expected motor responds. Do not skip this.
Confirm ESC status is arriving from every node, with RPM and current that track what the motor is doing.
## Troubleshooting
| Symptom | Check |
| --------------------------------------------------- | ---------------------------------------------------------------------------------------------- |
| Node does not appear on the bus | CAN Mode set to `UAVCAN` and written? Baud rate matching? CAN H/L not swapped? Bus terminated? |
| Two nodes conflict or drop out | Duplicate Controller ID. Each node needs a unique ID. |
| Wrong motor responds | ESC index does not match the flight controller's motor ordering. |
| No response to throttle, node visible | ESC index higher than the length of the command array the flight controller sends. |
| Motor reverses instead of braking | Raw mode is `Current`. Switch to `Current, no reverse brake`. |
| RPM mode does nothing | `UAVCAN Raw RPM Max` not set — full scale is zero. |
| Reported current looks wrong | Status Current Mode is set to Motor where the flight controller expects Input, or the reverse. |
| VESC Tool cannot reach a second controller over CAN | Expected in UAVCAN mode. Connect over USB. |
## Related
PPM, ADC, UART, and the Setup Input wizard.
Current limits and cutoffs — set these before commanding from a bus.