> 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/flight-controller/jetson-pabs/ark-jetson-pab-carrier/hardware/gpio-control.md).

# GPIO Control

The I2S0 connector pins come up as general-purpose GPIOs by default — no overlay or jetson-io step is needed. At idle the SoC drives none of them: the four output-capable pins sit hi-z, held HIGH by 604Ω pull-ups on the carrier, and DIN is a floating input. A pin wired to a relay or actuator never transitions at boot.

## I2S0 Connector Pin Mapping

| ARK Pin | Signal           | 40-Pin Header | libgpiod Name | Idle at Boot  |
| ------- | ---------------- | ------------- | ------------- | ------------- |
| 1       | VDD\_5V\_JPERIPH | -             | -             | -             |
| 2       | I2S0\_DOUT\_3V3  | Pin 40        | `PI.00`       | HIGH (pulled) |
| 3       | I2S0\_DIN\_3V3   | Pin 38        | `PI.01`       | hi-z (input)  |
| 4       | I2S0\_LRCLK\_3V3 | Pin 35        | `PI.02`       | HIGH (pulled) |
| 5       | I2S0\_SCLK\_3V3  | Pin 12        | `PH.07`       | HIGH (pulled) |
| 6       | AUD\_MCLK\_3V3   | Pin 7         | `PAC.06`      | HIGH (pulled) |
| 7       | GND              | -             | -             | -             |

Confirm the lines are exposed:

```bash
sudo gpioinfo | grep -E '"P(H\.07|I\.0[0-2]|AC\.06)"'
```

## Using the GPIOs

Drive and read the lines with `libgpiod` (`gpioset` / `gpioget`) or the Jetson.GPIO Python library. Jetson.GPIO addresses pins by their 40-pin header number and needs version 2.1.12 or newer:

```bash
sudo pip3 install 'Jetson.GPIO>=2.1.12'
```

The example below jumpers HDR40 pin 40 (DOUT) to pin 38 (DIN) and toggles HIGH/LOW, reading each transition back as a loopback test:

```python
import time
import Jetson.GPIO as GPIO

GPIO.setmode(GPIO.BOARD)
GPIO.setup(40, GPIO.OUT, initial=GPIO.LOW)  # I2S0_DOUT
GPIO.setup(38, GPIO.IN)                     # I2S0_DIN

try:
    for level in (GPIO.HIGH, GPIO.LOW, GPIO.HIGH, GPIO.LOW):
        GPIO.output(40, level)
        time.sleep(0.2)
        got = GPIO.input(38)
        print(f"wrote {level} read {got} {'PASS' if got == level else 'FAIL'}")
finally:
    GPIO.cleanup()
```

ARK-OS ships a complete version of this loopback as `i2s_gpio_example.py` (on `PATH`).

{% hint style="warning" %}
**GPIO state after your app exits**

While your app owns a line, the kernel guarantees its value. On release (clean exit, crash, or kill), **the pin retains its last-written value** until the next reboot re-asserts the pulled-HIGH idle state. If a line must be safe-off for an active-high load, add an external pull-down or keep a process owning the line (`gpioset --mode=signal`).
{% endhint %}

For the full pin reference, electrical details, and safe-state patterns, see the [ARK Jetson Kernel GPIO docs](https://github.com/ARK-Electronics/ark_jetson_kernel/blob/main/docs/gpio.md).


---

# 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 dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://docs.arkelectron.com/products/flight-controller/jetson-pabs/ark-jetson-pab-carrier/hardware/gpio-control.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

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.