> For the complete documentation index, see [llms.txt](https://docs.arkelectron.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.arkelectron.com/products/sensor/ark-cannode/ardupilot-instructions.md).

# ArduPilot Instructions

Guide for setting up an ARK CANnode as a PWM servo expander with ArduPilot AP\_Periph firmware, including gripper/dropper configuration.

The ARK CANnode can run [ArduPilot AP\_Periph](https://ardupilot.org/dev/docs/ap-peripheral-landing-page.html) firmware, enabling it to act as a DroneCAN peripheral node for expanding servo outputs, ESC control, and sensor connectivity over CAN.

## Flight Controller Setup

Flash your ARK flight controller with ArduPilot firmware using [QGroundControl](https://qgroundcontrol.com/) over USB.

Set the following parameters on the flight controller and reboot:

| Parameter         | Value | Description              |
| ----------------- | ----- | ------------------------ |
| `CAN_P1_DRIVER`   | 1     | Enable first CAN driver  |
| `CAN_D1_PROTOCOL` | 1     | Set protocol to DroneCAN |

Connect the CANnode to the flight controller's CAN bus and flash it with AP\_Periph firmware as described in [ArduPilot Firmware](/products/sensor/ark-cannode/firmware.md#ardupilot-firmware).

## Gripper/Dropper Setup

This example configures the first CANnode PWM output as a servo gripper for a dropping mechanism.

### Flight Controller Parameters

| Parameter          | Value | Description                                       |
| ------------------ | ----- | ------------------------------------------------- |
| `CAN_D1_UC_SRV_BM` | 1     | Enable Servo Channel 1 over CAN (bitmask bit 0)   |
| `SERVO1_FUNCTION`  | 28    | Gripper                                           |
| `GRIP_ENABLE`      | 1     | Enable gripper                                    |
| `GRIP_TYPE`        | 0     | Servo                                             |
| `GRIP_GRAB`        | 1000  | PWM value for grab/close (adjust to your servo)   |
| `GRIP_RELEASE`     | 1200  | PWM value for release/open (adjust to your servo) |
| `BRD_SAFETY_MASK`  | 1     | Allow Servo Channel 1 to output with safety on    |

{% hint style="warning" %}
After setting `GRIP_ENABLE = 1`, a reboot is required before the other `GRIP_*` parameters will appear.
{% endhint %}

{% hint style="info" %}
`CAN_D1_UC_SRV_BM` defaults to 0, meaning no servo commands are sent over CAN. This is the most commonly missed parameter.
{% endhint %}

### CANnode Parameters

The defaults should work without changes. The CANnode output functions map to flight controller servo channels by default (OUT1 maps to FC Servo 1, OUT2 to Servo 2, etc.).

{% hint style="info" %}
The `OUT*` parameters are accessed through the DroneCAN parameter interface. In the DroneCAN GUI Tool, double-click the CANnode and click **Fetch All** to view them.
{% endhint %}

### Triggering the Gripper

#### Via RC

Assign a switch on your transmitter to control the gripper:

| Parameter    | Value | Description     |
| ------------ | ----- | --------------- |
| `RCx_OPTION` | 19    | Gripper Release |

Replace `x` with the RC channel number mapped to your desired switch.

#### Via MAVLink

The gripper can also be controlled programmatically using `MAV_CMD_DO_GRIPPER`. The following Python script sends gripper open/close commands over USB:

{% file src="/files/Zbeb1mRzovk0YXiSp7dB" %}

Usage:

```bash
python3 gripper_cmd.py open
python3 gripper_cmd.py close
```

The script auto-detects ARK flight controllers connected via USB. Use `--port` to specify a device manually:

```bash
python3 gripper_cmd.py open --port /dev/ttyACM0
```

## Using Multiple Servos

To use the first 3 CANnode outputs, set `CAN_D1_UC_SRV_BM = 7` (bits 0, 1, 2) and configure `SERVO1_FUNCTION`, `SERVO2_FUNCTION`, and `SERVO3_FUNCTION` on the flight controller. Update `BRD_SAFETY_MASK` accordingly (e.g., 7 for channels 1-3).


---

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