> 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/accessories/ark-servo-expander/hardware.md).

# Hardware Reference

## Specifications

| Specification  | Value                                                     |
| -------------- | --------------------------------------------------------- |
| PWM controller | [NXP PCA9685](https://www.nxp.com/products/PCA9685)       |
| Outputs        | 16 PWM channels on two 8-channel 10-pin JST-GH connectors |
| Interface      | I2C, 4-pin JST-GH                                         |
| Dimensions     | 1.875 × 1.65 × 0.675 cm                                   |
| Weight         | 2 g                                                       |

## Pinout

The [ARK Servo Adapter](https://arkelectron.com/product/servo-adapter/) breaks a 10-pin PWM connector out to 3-pin servo headers.

### PWM CH0–CH7 — 10-pin JST-GH

| Pin | Signal        | Voltage       |
| --- | ------------- | ------------- |
| 1   | VDD\_SERVO\_1 | VDD\_SERVO\_1 |
| 2   | CH0\_EXT      | +3.3V         |
| 3   | CH1\_EXT      | +3.3V         |
| 4   | CH2\_EXT      | +3.3V         |
| 5   | CH3\_EXT      | +3.3V         |
| 6   | CH4\_EXT      | +3.3V         |
| 7   | CH5\_EXT      | +3.3V         |
| 8   | CH6\_EXT      | +3.3V         |
| 9   | CH7\_EXT      | +3.3V         |
| 10  | GND           | GND           |

### PWM CH8–CH15 — 10-pin JST-GH

| Pin | Signal        | Voltage       |
| --- | ------------- | ------------- |
| 1   | VDD\_SERVO\_2 | VDD\_SERVO\_2 |
| 2   | CH8\_EXT      | +3.3V         |
| 3   | CH9\_EXT      | +3.3V         |
| 4   | CH10\_EXT     | +3.3V         |
| 5   | CH11\_EXT     | +3.3V         |
| 6   | CH12\_EXT     | +3.3V         |
| 7   | CH13\_EXT     | +3.3V         |
| 8   | CH14\_EXT     | +3.3V         |
| 9   | CH15\_EXT     | +3.3V         |
| 10  | GND           | GND           |

### I2C — 4-pin JST-GH

| Pin | Signal   | Voltage |
| --- | -------- | ------- |
| 1   | 5V\_IN   | +5.0V   |
| 2   | I2C\_SCL | +3.3V   |
| 3   | I2C\_SDA | +3.3V   |
| 4   | GND      | GND     |

## Resistor Settings

VDD\_SERVO\_1 and VDD\_SERVO\_2 can be connected together by shorting the pads of the large unpopulated resistor. Either with solder or a 0 Ohm 0805 resistor.

The I2C address can be changed by moving the resistors from the left position to the right position to change the bit from 0 to 1.

<figure><img src="https://1515919775-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FOwmEn1N45AR4WjMQhHlu%2Fuploads%2FSSK4y1ez2QZFJShjEJzD%2FBottom%20Settings.png?alt=media&amp;token=07d9fe6c-ead5-4b6c-adee-5d744d369a1e" alt=""><figcaption></figcaption></figure>

## 3D Model and Case

| File                                                                                                                          | Contents |
| ----------------------------------------------------------------------------------------------------------------------------- | -------- |
| [Servo\_Expander.step](https://github.com/ARK-Electronics/ark-hardware/raw/main/ARK_Servo_Expander/model/Servo_Expander.step) | Board    |

All files: [ARK\_Servo\_Expander in ark-hardware](https://github.com/ARK-Electronics/ark-hardware/tree/main/ARK_Servo_Expander)


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