> 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/ark-pi6x-flow/firmware.md).

# Firmware

The flight controller runs PX4 1.15 or later, or ArduPilot 4.7 or later. The AFBR-S50LV85D distance sensor on the Pi6X Flow is not supported in ArduPilot.

| Firmware  | Build target                                                                                                     |
| --------- | ---------------------------------------------------------------------------------------------------------------- |
| PX4       | `ark_pi6x_default` ([boards/ark/pi6x](https://github.com/PX4/PX4-Autopilot/tree/main/boards/ark/pi6x))           |
| ArduPilot | `ARK_PI6X` ([hwdef](https://github.com/ArduPilot/ardupilot/tree/master/libraries/AP_HAL_ChibiOS/hwdef/ARK_PI6X)) |

The flight controller's USB connects only to the Pi, so firmware is updated from the Pi.

## From the Web UI

Open the [ARK-UI](http://pi6x.local) **Autopilot** page, select the **Firmware** tab, and upload a `.px4` (PX4) or `.apj` (ArduPilot) firmware file.

<figure><img src="https://1515919775-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FOwmEn1N45AR4WjMQhHlu%2Fuploads%2Fgit-blob-3fee3fa2ab27bf9c23b532d753dcb6174701c8b5%2Fark-ui-autopilot-firmware-pi6x.png?alt=media" alt=""><figcaption></figcaption></figure>

## From the Command Line

SSH into the Pi and run the ARK-OS flashing tool (on `PATH`). The update is performed over the USB connection:

```bash
flash_firmware.sh <firmware.px4>
```

## Downloads

* PX4: `ark_pi6x_default.px4` from the [PX4 releases page](https://github.com/PX4/PX4-Autopilot/releases/)
* ArduPilot: [firmware.ardupilot.org](https://firmware.ardupilot.org/), board `ARK_PI6X`

## Bootloader Recovery

If the flight controller does not enumerate over USB, recover the bootloader over SWD on the flight controller debug port: [ST-LINK Flashing Guide](/knowledge-base/knowledge-base/st-link-flashing-guide.md#flashing-px4-flight-controllers).


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