> 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/embedded-computers/ark-just-a-pi/hardware.md).

# Hardware Reference

## Specifications

| Specification  | Value                                                                                                                                                                                                          |
| -------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Compute module | Raspberry Pi [Compute Module 5](https://www.raspberrypi.com/products/compute-module-5/); [Compute Module 4](https://www.raspberrypi.com/products/compute-module-4/) with the [limits below](#compute-module-4) |
| Storage        | microSD slot for Lite modules (no eMMC); modules with eMMC boot from their eMMC                                                                                                                                |
| Ethernet       | Built-in switch with two 100 Mbps ports (4-pin JST-GH)                                                                                                                                                         |
| USB            | USB-C, dual role, USB 3.0; 4-pin JST-GH, USB 2.0                                                                                                                                                               |
| Cameras        | 2× MIPI CSI, 22-pin 0.5 mm FFC, Raspberry Pi 5 CSI pinout                                                                                                                                                      |
| PCIe           | PCIe x1, 16-pin FFC, Raspberry Pi 5 PCIe pinout                                                                                                                                                                |
| Display        | Micro HDMI                                                                                                                                                                                                     |
| UARTs and GPIO | UART0 debug/GPIO, UART2/SPI3/GPIO, UART3/SPI4/GPIO, UART4/PWM/GPIO (6-pin JST-GH each)                                                                                                                         |
| Fan            | 4-pin JST-SH, Raspberry Pi 5 fan pinout                                                                                                                                                                        |
| Power          | 5 V, 2 A minimum, through a 6-pin Molex CLIK-Mate with I2C that matches [ARK PAB power modules](https://arkelectron.com/product-category/power/)                                                               |

## Compute Module 4

A CM4 fits, but these interfaces don't work with it:

* CAM2 (MIPI1)
* UART2
* USB-C
* PCIe
* Fan

With a CM4, the camera on CAM1 is the overlay default in `config.txt` (no `cam0` parameter), and the UART3 and UART4 connectors are uart4 (`/dev/ttyAMA4`) and uart5 (`/dev/ttyAMA5`).

## PCIe

* Gen 2 (default, tested). Set `dtparam=pciex1_gen=3` in [`config.txt`](/products/embedded-computers/ark-just-a-pi/flashing-guide/after-flashing-before-installing.md) for Gen 3 (untested).
* The 5 V pins are fed through a load switch limited to 1.5 A. The Compute Module's `PCIE_PWR_EN` turns the switch on and is also routed to pin 13, so the adapter can use it to enable its own regulator.

## Pinout

<figure><img src="https://1515919775-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FOwmEn1N45AR4WjMQhHlu%2Fuploads%2FKSXEGBBMW4v3fStprM68%2FPinout%20Drawing%20Top.png?alt=media&amp;token=d133d601-49b3-47b4-b93b-dd9cff60fb35" alt=""><figcaption></figcaption></figure>

<figure><img src="https://1515919775-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FOwmEn1N45AR4WjMQhHlu%2Fuploads%2F4BbVhsd5eOKF90ylCa1f%2FPinout%20Drawing%20Bottom.png?alt=media&amp;token=11819837-421f-4d8d-81e6-ef4dc2bdd1b4" alt=""><figcaption></figcaption></figure>

{% file src="/files/rEk5tGTkkooCudUB5EDI" %}

### Power — 6-pin 2.00 mm Molex [CLIK-Mate 502443](https://www.molex.com/en-us/part-list/502443)

Mating plug [5024390600](https://www.digikey.com/en/products/detail/molex/5024390600/2380425)

Pre-crimped wires [0797581014](https://www.digikey.com/en/products/detail/molex/0797581014/6346648)

| Pin | Signal             | Voltage |
| --- | ------------------ | ------- |
| 1   | VDD\_5V\_IN        | 5.0V    |
| 2   | VDD\_5V\_IN        | 5.0V    |
| 3   | PI\_SCL1\_PWR\_EXT | 3.3V    |
| 4   | PI\_SDA1\_PWR\_EXT | 3.3V    |
| 5   | GND                | GND     |
| 6   | GND                | GND     |

### Fan — 4-pin JST-SH

| Pin | Signal      | Voltage      |
| --- | ----------- | ------------ |
| 1   | VDD\_5V\_IN | 5.0V (500mA) |
| 2   | FAN\_PWM    | 5.0V         |
| 3   | GND         | GND          |
| 4   | FAN\_TACHO  | 5.0V         |

### UART0 Debug/GPIO — 6-pin JST-GH

| Pin | Signal            | Voltage      |
| --- | ----------------- | ------------ |
| 1   | VDD\_5V\_IN       | 5.0V (500mA) |
| 2   | UART0\_TX/GPIO14  | 3.3V         |
| 3   | UART0\_RX/GPIO15  | 3.3V         |
| 4   | UART0\_CTS/GPIO16 | 3.3V         |
| 5   | UART0\_RTS/GPIO17 | 3.3V         |
| 6   | GND               | GND          |

### UART2/SPI3/GPIO — 6-pin JST-GH

| Pin | Signal                      | Voltage      |
| --- | --------------------------- | ------------ |
| 1   | VDD\_5V\_IN                 | 5.0V (500mA) |
| 2   | UART2\_TXD/SPI3\_CSn/GPIO4  | 3.3V         |
| 3   | UART2\_RXD/SPI3\_MISO/GPIO5 | 3.3V         |
| 4   | UART2\_CTS/SPI3\_MOSI/GPIO6 | 3.3V         |
| 5   | UART2\_RTS/SPI3\_SCLK/GPIO7 | 3.3V         |
| 6   | GND                         | GND          |

### UART3/SPI4/GPIO — 6-pin JST-GH

| Pin | Signal                       | Voltage      |
| --- | ---------------------------- | ------------ |
| 1   | VDD\_5V\_IN                  | 5.0V (500mA) |
| 2   | UART3\_TXD/SPI4\_CSn/GPIO8   | 3.3V         |
| 3   | UART3\_RXD/SPI4\_MISO/GPIO9  | 3.3V         |
| 4   | UART3\_CTS/SPI4\_MOSI/GPIO10 | 3.3V         |
| 5   | UART3\_RTS/SPI4\_SCLK/GPIO11 | 3.3V         |
| 6   | GND                          | GND          |

### UART4/PWM/GPIO — 6-pin JST-GH

| Pin | Signal                 | Voltage      |
| --- | ---------------------- | ------------ |
| 1   | VDD\_5V\_IN            | 5.0V (500mA) |
| 2   | UART4\_TXD/PWM0/GPIO12 | 3.3V         |
| 3   | UART4\_RXD/PWM1/GPIO13 | 3.3V         |
| 4   | PWM2/GPIO18            | 3.3V         |
| 5   | PWM3/GPIO19            | 3.3V         |
| 6   | GND                    | GND          |

### CAM1 (MIPI0) — 22-pin 0.5 mm FFC

| Pin | Signal           | Voltage   |
| --- | ---------------- | --------- |
| 1   | GND              | GND       |
| 2   | MIPI0\_D0\_N     | 1.2V      |
| 3   | MIPI0\_D0\_P     | 1.2V      |
| 4   | GND              | GND       |
| 5   | MIPI0\_D1\_N     | 1.2V      |
| 6   | MIPI0\_D1\_P     | 1.2V      |
| 7   | GND              | GND       |
| 8   | MIPI0\_C\_N      | 1.2V      |
| 9   | MIPI0\_C\_P      | 1.2V      |
| 10  | GND              | GND       |
| 11  | MIPI0\_D2\_N     | 1.2V      |
| 12  | MIPI0\_D2\_P     | 1.2V      |
| 13  | GND              | GND       |
| 14  | MIPI0\_D3\_N     | 1.2V      |
| 15  | MIPI0\_D3\_P     | 1.2V      |
| 16  | GND              | GND       |
| 17  | CAM\_GPIO0       | 3.3V      |
| 18  | CAM\_GPIO1       | 3.3V      |
| 19  | GND              | GND       |
| 20  | SCL0             | 3.3V      |
| 21  | SDA0             | 3.3V      |
| 22  | VDD\_3V3\_CAMERA | 3.3V (1A) |

### CAM2 (MIPI1) — 22-pin 0.5 mm FFC

| Pin | Signal                                  | Voltage   |
| --- | --------------------------------------- | --------- |
| 1   | GND                                     | GND       |
| 2   | MIPI1\_D0\_N                            | 1.2V      |
| 3   | MIPI1\_D0\_P                            | 1.2V      |
| 4   | GND                                     | GND       |
| 5   | MIPI1\_D1\_N                            | 1.2V      |
| 6   | MIPI1\_D1\_P                            | 1.2V      |
| 7   | GND                                     | GND       |
| 8   | MIPI1\_C\_N                             | 1.2V      |
| 9   | MIPI1\_C\_P                             | 1.2V      |
| 10  | GND                                     | GND       |
| 11  | MIPI1\_D2\_N                            | 1.2V      |
| 12  | MIPI1\_D2\_P                            | 1.2V      |
| 13  | GND                                     | GND       |
| 14  | MIPI1\_D3\_N                            | 1.2V      |
| 15  | MIPI1\_D3\_P                            | 1.2V      |
| 16  | GND                                     | GND       |
| 17  | Pulled up to 3.3V via 1.5k Ohm Resistor | 3.3V      |
| 18  | NC                                      | NC        |
| 19  | GND                                     | GND       |
| 20  | ID\_SC                                  | 3.3V      |
| 21  | ID\_SD                                  | 3.3V      |
| 22  | VDD\_3V3\_CAMERA                        | 3.3V (1A) |

### USB 2.0 — 4-pin JST-GH

| Pin | Signal     | Voltage   |
| --- | ---------- | --------- |
| 1   | USB2\_VBUS | 5.0V (1A) |
| 2   | USB2\_N    | 3.3V      |
| 3   | USB2\_P    | 3.3V      |
| 4   | GND        | GND       |

### ETH1 — 4-pin JST-GH

| Pin | Signal           | Voltage  |
| --- | ---------------- | -------- |
| 1   | EXT1\_ETH\_RX\_N | Isolated |
| 2   | EXT1\_ETH\_RX\_P | Isolated |
| 3   | EXT1\_ETH\_TX\_N | Isolated |
| 4   | EXT1\_ETH\_TX\_P | Isolated |

### ETH2 — 4-pin JST-GH

| Pin | Signal           | Voltage  |
| --- | ---------------- | -------- |
| 1   | EXT2\_ETH\_RX\_N | Isolated |
| 2   | EXT2\_ETH\_RX\_P | Isolated |
| 3   | EXT2\_ETH\_TX\_N | Isolated |
| 4   | EXT2\_ETH\_TX\_P | Isolated |

### PCIe — 16-pin FFC (CF20161V0R0-NH)

| Pin | Signal         | Voltage     |
| --- | -------------- | ----------- |
| 1   | 5V\_PCIE\_FFC  | 5.0V (1.5A) |
| 2   | 5V\_PCIE\_FFC  | 5.0V (1.5A) |
| 3   | GND            | GND         |
| 4   | PCIE\_CLK\_P   | 1.0V        |
| 5   | PCIE\_CLK\_N   | 1.0V        |
| 6   | GND            | GND         |
| 7   | PCIE\_RX\_P    | 1.0V        |
| 8   | PCIE\_RX\_N    | 1.0V        |
| 9   | GND            | GND         |
| 10  | PCIE\_TX\_P    | 1.0V        |
| 11  | PCIE\_TX\_N    | 1.0V        |
| 12  | GND            | GND         |
| 13  | PCIE\_PWR\_EN  | 3.3V        |
| 14  | PCIE\_WAKEn    | 3.3V        |
| 15  | PCIE2\_CLKREQn | 3.3V        |
| 16  | PCIE2\_RSTn    | 3.3V        |

## Block Diagram

<figure><img src="https://1515919775-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FOwmEn1N45AR4WjMQhHlu%2Fuploads%2F0onoAQYUyLd7INg8SGfE%2FPi_CM5_Carrier.drawio.png?alt=media&amp;token=5798848d-1399-406c-9abc-047da75b45fd" alt=""><figcaption><p>ARK Just a Pi Block Diagram</p></figcaption></figure>

## 3D Model and Case

| File                                                                                                                                               | Contents                  |
| -------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------- |
| [ARK\_Just\_a\_Pi.step](https://github.com/ARK-Electronics/ark-hardware/raw/main/ARK_Just_A_Pi/model/ARK_Just_a_Pi.step)                           | Board model               |
| [Bottom\_Just\_a\_Pi\_Case.step](https://github.com/ARK-Electronics/ark-hardware/raw/main/ARK_Just_A_Pi/case/Bottom_Just_a_Pi_Case.step)           | Case bottom               |
| [Fan\_Top\_Just\_a\_Pi\_Case.step](https://github.com/ARK-Electronics/ark-hardware/raw/main/ARK_Just_A_Pi/case/Fan_Top_Just_a_Pi_Case.step)        | Case top with fan opening |
| [No\_Fan\_Top\_Just\_a\_Pi\_Case.step](https://github.com/ARK-Electronics/ark-hardware/raw/main/ARK_Just_A_Pi/case/No_Fan_Top_Just_a_Pi_Case.step) | Case top without fan      |

All files: [ARK\_Just\_A\_Pi in ark-hardware](https://github.com/ARK-Electronics/ark-hardware/tree/main/ARK_Just_A_Pi)


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation by asking a question.

Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters:

```
GET https://docs.arkelectron.com/products/embedded-computers/ark-just-a-pi/hardware.md?ask=<question>&goal=<user_goal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.