# Flash Bootloader

## Flashing Bootloader via AM32

You can update the bootloader using the [AM32 Configurator](https://am32.ca/configurator). Once connected select "Flash firmware" and select the "Bootloader" tab. Download the **AM32-bootloader-updaters-amj.zip** from the [AM32-bootloader release artifacts](https://github.com/am32-firmware/AM32-bootloader/releases). Select the **AM32\_F051\_BL\_UPDATER\_PB4\_V15.amj.**

***

## Flashing Bootloader via SWD

If you're flashing an ESC without firmware or the firmware has become corrupted, you can reflash the ESC with SWD to bring it back to a fresh state.

For detailed instructions on ST-LINK setup, software installation, and usage, see the [ST-LINK Flashing Guide](/knowledge-base/knowledge-base/st-link-flashing-guide.md).

#### What You'll Need

* ARK 4IN1 ESC
* ST-LINK V3 Mini (recommended) or ST-LINK V2
* Computer running Windows or Ubuntu
* [AM32 bootloader file](/products/electronic-speed-controller/ark-4in1-esc/firmware.md#am32-bootloader-firmware)

#### Hardware Setup

The ARK 4IN1 ESC has 4 separate STM32F051 microcontrollers (one per motor channel), each with their own SWD interface on a single 10-pin debug connector. See the [pinout](/products/electronic-speed-controller/ark-4in1-esc/pinout.md) for the full connector diagram.

| Pin | Signal          |
| --- | --------------- |
| 1   | 3.3V            |
| 2   | SWDIO 1 (ESC 1) |
| 3   | SWCLK 1 (ESC 1) |
| 4   | SWDIO 2 (ESC 2) |
| 5   | SWCLK 2 (ESC 2) |
| 6   | SWDIO 3 (ESC 3) |
| 7   | SWCLK 3 (ESC 3) |
| 8   | SWDIO 4 (ESC 4) |
| 9   | SWCLK 4 (ESC 4) |
| 10  | GND             |

To flash each ESC, connect your ST-LINK to the corresponding SWDIO/SWCLK pair. For example, to flash ESC 1:

| ST-LINK Pin     | Debug Connector Pin | Signal  |
| --------------- | ------------------- | ------- |
| SWDIO           | Pin 2               | SWDIO 1 |
| SWCLK           | Pin 3               | SWCLK 1 |
| GND             | Pin 10              | GND     |
| 3.3V (optional) | Pin 1               | 3.3V    |

{% hint style="warning" %}
If your ESC is powered from a battery or power supply, **do not** connect the 3.3V line from the ST-LINK.
{% endhint %}

Repeat the process for ESC 2-4 using their respective SWDIO/SWCLK pins (4/5, 6/7, 8/9).

#### Flash the Bootloader

Flash each ESC MCU with the bootloader binary:

```bash
st-flash write AM32_F051_BOOTLOADER_PB4.bin 0x08000000
```


---

# Agent Instructions: 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:

```
GET https://docs.arkelectron.com/products/electronic-speed-controller/ark-4in1-esc/firmware/flash-bootloader.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
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.