docs/development/hardware/khadas-vim3.md - fuchsia - Git at Google

 # Install Fuchsia on a Khadas VIM3 board

 This guide shows you how to install Fuchsia on a
 [Khadas VIM3](https://www.khadas.com/vim3). The installation
 process will probably take between 1 to 3 hours.

 Running Fuchsia on VIM3 is useful if you want to explore how Fuchsia works on
 relatively low-cost real hardware that supports many kinds of peripheral devices.
 See [Appendix: Feature support](#features) for details on which VIM3 features
 Fuchsia supports.

 If you just want to explore Fuchsia with the lowest friction possible, check out
 [Get started with the Fuchsia SDK](/docs/get-started/sdk/index.md) instead.

 See [Appendix: Support](#support) if you have any trouble completing
 this guide.

 ## Audience {#audience}

 If you've never tinkered with electronics you might find this
 guide difficult to complete. For example, this guide assumes that you know
 how to hook up serial cable wires to GPIOs to read logs and send commands
 over a serial communication program.

 This guide also assumes that you're comfortable
 with CLI workflows such as building Fuchsia from source.

 ## Prerequisites {#prerequisites}

 You'll need all of the following hardware and software to complete this guide:

 * A [Khadas VIM3](https://www.khadas.com/vim3) single-board computer.

   Caution: It's unknown whether Fuchsia will run on the Basic model VIM3.
   This guide was validated with the Pro model VIM3.

 * A desktop or laptop computer that's running Linux and has 2 USB ports
   available.

   Key Term: This desktop or laptop is called the **host**
   throughout the rest of this guide.

   Caution: A macOS host may work but these instructions have not been validated
   with macOS. Building Fuchsia on a remote Linux computer and then attempting to flash
   Fuchsia onto the VIM3 with a local macOS host is known to not work.

   <!-- Context from kayce@: Local macOS host + remote Linux workstation doesn't work because
        when you run `fx pave` you get an error about a mismatch between the local
        host OS and the remote workstation OS. -->

   Note: This guide assumes that your Linux distribution has Debian commands
   like `apt`.

 * A power supply of at least 24W to your host. The VIM3 can draw that much power when
   [DVFS](https://en.wikipedia.org/wiki/Dynamic_frequency_scaling) is enabled.

 * A working Fuchsia development environment on your host. In other words you
   should be able to build Fuchsia from its source code on your host. See
   [Build Fuchsia](#build).

 * A [USB to TTL serial cable](https://www.adafruit.com/product/954).

 * A USB-C to USB-\* cable that supports both data and power delivery.
   The USB-C side is for the VIM3. The other side can be whatever USB
   type your host supports.

 The following is optional:

 * A [heatsink](https://www.khadas.com/product-page/new-vim-heatsink).
   This enables running 2 CPU cores on the VIM3 at full speed without
   reaching 80°C, the critical temperature beyond which cores are throttled
   down.

 See the [VIM3 collection](https://www.khadas.com/shop?Collection=VIM3&sort=price_descending)
 in the Khadas shop for examples of compatible accessories.

 Note: All the links in this section are only for your convenience. You
 don't need to buy from these exact stores or these exact parts.

 ## Build Fuchsia {#build}

 If you don't already have an [in-tree][glossary.in-tree] environment
 set up, you should start the process now because it can take a while to
 complete:

 1. [Download the Fuchsia source code](/docs/get-started/get_fuchsia_source.md).

 1. [Configure and build Fuchsia](/docs/get-started/build_fuchsia.md).

    * When building Fuchsia, use `fx set core.vim3` instead.

 Note: The rest of this guide assumes that your Fuchsia source code directory
 is located at `~/fuchsia`.

 Important: Whenever you see an `fx` command this guide assumes that your
 working directory is within your in-tree Fuchsia source code checkout.
 In other words this guide assumes that you run `cd ~/fuchsia` before
 running any `fx` commands.

 You'll use the Fuchsia development environment to build the Fuchsia image
 for VIM3 and run an in-tree CLI tool for flashing the Fuchsia image onto
 the VIM3.

 ## Set up the hardware {#hardware}

 Set up the VIM3 to communicate with your host:

 1. Connect the VIM3 and your host to each other with the USB-C to USB-\* cable.
    The white LED on the VIM3 should turn on.

    Caution: Don't put a [USB hub](https://en.wikipedia.org/wiki/USB_hub)
    between the VIM3 and your host. The hub may make it harder for your
    VIM3 and host to detect and communicate with each other.

    This connection is used to power and flash the VIM3 with
    [`fastboot`](https://en.wikipedia.org/wiki/Fastboot).

 1. Connect the serial cable wires to the VIM3's GPIOs:

    * GND to pin 17.

    * RX (in to VIM3) to pin 18.

    * TX (out from VIM3) to pin 19.

    * Don't connect the power wire of your serial cable to any VIM3 GPIO.
      The VIM3 is getting power through the USB cable.

    Tip: Pins 1, 20, 21, and 40 are labeled on the circuit board.

    Caution: In general the colors for TX and RX wires are not standardized.
    For example your RX wire may be blue or green.

    See [Serial Debugging Tool](https://docs.khadas.com/products/sbc/vim3/development/setup-serial-tool)
    for an example image of how your serial wires should be connected to the VIM3.

 ### Verify the serial connection {#serial}

 Make sure that you can view the logs being sent over the serial cable:

 1. Open Fuchsia's serial console:

    ```posix-terminal
    fx serial
    ```

    Note: If `fx serial` detects multiple USB devices and you don't know which one to use,
    try disconnecting the serial cable from your host, running `ls /dev/ttyUSB*`,
    then re-connecting the serial cable and running the command again. If you see
    no difference when running `ls /dev/ttyUSB*` try `ls /dev/tty*` or `ls /dev/*` instead.

 1. Press the reset button on the VIM3. The reset button is the one with the **R**
    printed next to it on the circuit board.
    See [VIM3/3L Hardware](https://docs.khadas.com/products/sbc/vim3/hardware/start) for
    a diagram. In your serial console you should see human-readable logs.

 ## Erase the eMMC {#emmc}

 In later sections of this guide you'll update the bootloader and
 OS on the VIM3. These updates don't work unless you
 completely erase the eMMC first:

 1. Press the reset button on your VIM3.

 1. Right after you press the reset button, start repeatedly pressing the
    <kbd>Space</kbd> key as your VIM3 boots up. Make sure that your cursor
    is focused on your serial console. The bootloader process should pause
    and your serial console should show a `kvim3#` prompt. Your serial
    console is now providing you access to the **U-Boot shell**.

 1. Run the following command in the U-Boot shell:

    ```posix-terminal
    store init 3
    ```

    Your serial console logs should verify that the eMMC was correctly erased.

 See [Erase eMMC](https://docs.khadas.com/products/sbc/vim3/development/erase-emmc)
 for more details.

 ## Update the Android image on the VIM3 {#android}

 <!-- Context: https://forum.khadas.com/t/unable-to-change-bootloader-for-vim3/12708/6 -->

 The Android image that ships by default on the VIM3 does
 not support Fuchsia installation. If you just received your VIM3
 from Khadas you must update your Android image:

 1. Click the following URL to download the updated Android image:
    <https://dl.khadas.com/firmware/vim3/android/VIM3_Pie_V210527.7z>

 1. Extract the compressed archive file (`VIM3_Pie_V210527.7z`).
    After the extraction you should have a `VIM3_Pie_V210527` directory
    with an `update.img` file in it.

 1. Follow the instructions in [Install OS into
    eMMC](https://docs.khadas.com/products/sbc/vim3/install-os/install-os-into-emmc-via-usb-tool).
    When running `aml-burn-tool` the value for the `-i` flag should be the
    path to your `update.img` file. Your command should look similar to this:

    ```posix-terminal
    aml-burn-tool -b VIM3 -i ~/Downloads/VIM3_Pie_V210527/update.img
    ```

    Caution: Make sure that you're following the instructions for Ubuntu
    and VIM3 by clicking the **Install on Ubuntu** and **VIM3/VIM3L** tabs.
    These instructions are not shown by default.

    Tip: The `TST Mode` workflow is probably the easiest and fastest way to get
    your VIM3 into Upgrade Mode.

 1. If the white and red LEDs on your VIM3 are off and the blue LED is on,
    it means that your VIM3 is in sleep mode. Try putting your VIM3
    back into [Upgrade Mode](https://docs.khadas.com/products/sbc/vim3/install-os/boot-into-upgrade-mode)
    and then pressing the reset button again.

 At this point the white LED on your VIM3 should be on and you should see
 logs in your serial console after you press the reset button on your VIM3.

 ## Update the bootloader {#bootloader}

 Flash Fuchsia's custom bootloader onto the VIM3:

 1. Access the U-Boot shell again by pressing the reset button and
    then repeatedly pressing the <kbd>Space</kbd> key in your serial
    console. When your serial console shows the `kvim3#` prompt, you're
    in the U-Boot shell.

 1. In your U-Boot shell run the following command:

    ```posix-terminal
    fastboot
    ```

    You should see the following logs in your serial console:

    ```
    g_dnl_register: g_dnl_driver.name = usb_dnl_fastboot

    USB RESET
    SPEED ENUM

    USB RESET
    SPEED ENUM
    ```

    If you see the first line (`g_dnl_register: g_dnl_driver.name = usb_dnl_fastboot`)
    but not the lines after that, try using a different USB-C to USB-\* cable and make
    sure that it supports both data and power delivery.

 1. Open a new terminal window in your host and run the following commands:

    ```posix-terminal
    cd ~/fuchsia/prebuilt/third_party/fastboot

    ./fastboot flashing unlock

    ./fastboot flashing unlock_critical

    ./fastboot flash bootloader ~/fuchsia/prebuilt/third_party/firmware/vim3/u-boot.bin.unsigned

    ./fastboot reboot
    ```

    Caution: Installing the Android SDK Platform Tools probably installed another
    instance of `fastboot` on your host. When working with Fuchsia, remember to use
    the [in-tree][glossary.in-tree] version of `fastboot` at
    `~/fuchsia/prebuild/third_party/fastboot/fastboot`. The `fastboot` protocol allows arbitrary
    vendor protocol extensions and Fuchsia may rely on this functionality in the future.

 Note: You can also build the custom bootloader (`u-boot.bin.unsigned`) from source:
 <https://third-party-mirror.googlesource.com/u-boot/+/refs/heads/vim3>

 ## Flash Fuchsia into the eMMC {#fuchsia}

 Complete these steps to install Fuchsia onto your VIM3 for the first time. You only
 need to do these steps once. Once you have Fuchsia running on your VIM3, the
 [Update your Fuchsia image](#update) workflow is a faster way to update the Fuchsia
 image on your VIM3.

 1. If you just ran the `./fastboot reboot` command from the last section then
    your VIM3 should already be in `fastboot` mode. You can check your `fx serial`
    logs to confirm. Otherwise press the reset button and then repeatedly press
    the <kbd>F</kbd> in your `fx serial` console until you see `USB RESET` and
    `SPEED ENUM` again.

    Important: You have to press the <kbd>F</kbd> key now to enter <code>fastboot</code>
    mode. Previously you pressed the <kbd>Space</kbd> key.

 1. From a separate terminal on your host run the following command:

    ```posix-terminal
    fx flash
    ```

 Your VIM3 is now running Fuchsia!

 ## Update your Fuchsia image {#update}

 Complete these steps when you already have Fuchsia running on your VIM3
 and want to update the Fuchsia image on your VIM3.

 1. Run the following command from a terminal on your host:

    ```posix-terminal
    fx serve
    ```

    Leave this command running.

 1. Make some changes in your in-tree Fuchsia checkout and build the changes.

 1. Open a new terminal window and perform an OTA update of the Fuchsia image on your VIM3:

    ```posix-terminal
    fx ota
    ```

 ## Appendix: Fix a bricked VIM3 {#bricks}

 Do these steps if you've [bricked](https://en.wikipedia.org/wiki/Brick_(electronics))
 your VIM3 and need to "factory reset" it:

 1. [Erase the eMMC](#emmc).
 1. [Update the Android image](#android).
 1. [Update the bootloader](#bootloader).
 1. [Flash Fuchsia into the eMMC](#fuchsia).

 ## Appendix: Support {#support}

 * For issues that seem related to VIM3 hardware or firmware, try the
   [VIM3 official docs](https://docs.khadas.com/linux/vim3/index.html) and
   [Khadas VIM3 official forum](https://forum.khadas.com/c/khadas-vim3/30).
 * For issues that seem related to Fuchsia, try the
   [Fuchsia mailing lists and chat rooms](/docs/contribute/community/mailing-lists.md).

 ## Appendix: Feature support {#features}

 Fuchsia currently supports these features of the VIM3:

 * UART Serial Debugger
 * Paving over ethernet and USB
 * Storage (eMMC)
 * HDMI Display and Framebuffer
 * GPU (Mali) and Vulkan graphics
 * Ethernet
 * SDIO
 * I2C
 * GPIO
 * Temperature Sensors and DVFS
 * RTC
 * Clock
 * Fan
 * NNA
 * USB-C in peripheral mode
 * USB-A

 These features are under development and may not be supported:

 * Video decoder
 * SPI
 * Audio

 The following features are not supported, but might be added by future
 contributions:

 * SPI Flash
 * USB-C in host mode
 * Power management and PMIC
 * Wake on LAN
 * UART BT

 These features are not supported and are unlikely to be added:

 * Video encoding (due to non-public firmware)
 * Trusted Execution Environment / secure boot

 ## Appendix: Update the boot splash screen {#splash}

 To update the boot splash screen to be the Fuchsia logo, run the following command
 from a host terminal while the VIM3 is in `fastboot` mode:

 ```posix-terminal
 fastboot flash logo ~/fuchsia/zircon/kernel/target/arm64/board/vim3/firmware/logo.img
 ```
	# Install Fuchsia on a Khadas VIM3 board

	This guide shows you how to install Fuchsia on a
	[Khadas VIM3](https://www.khadas.com/vim3). The installation
	process will probably take between 1 to 3 hours.

	Running Fuchsia on VIM3 is useful if you want to explore how Fuchsia works on
	relatively low-cost real hardware that supports many kinds of peripheral devices.
	See [Appendix: Feature support](#features) for details on which VIM3 features
	Fuchsia supports.

	If you just want to explore Fuchsia with the lowest friction possible, check out
	[Get started with the Fuchsia SDK](/docs/get-started/sdk/index.md) instead.

	See [Appendix: Support](#support) if you have any trouble completing
	this guide.

	## Audience {#audience}

	If you've never tinkered with electronics you might find this
	guide difficult to complete. For example, this guide assumes that you know
	how to hook up serial cable wires to GPIOs to read logs and send commands
	over a serial communication program.

	This guide also assumes that you're comfortable
	with CLI workflows such as building Fuchsia from source.

	## Prerequisites {#prerequisites}

	You'll need all of the following hardware and software to complete this guide:

	* A [Khadas VIM3](https://www.khadas.com/vim3) single-board computer.

	Caution: It's unknown whether Fuchsia will run on the Basic model VIM3.
	This guide was validated with the Pro model VIM3.

	* A desktop or laptop computer that's running Linux and has 2 USB ports
	available.

	Key Term: This desktop or laptop is called the host
	throughout the rest of this guide.

	Caution: A macOS host may work but these instructions have not been validated
	with macOS. Building Fuchsia on a remote Linux computer and then attempting to flash
	Fuchsia onto the VIM3 with a local macOS host is known to not work.

	<!-- Context from kayce@: Local macOS host + remote Linux workstation doesn't work because
	when you run `fx pave` you get an error about a mismatch between the local
	host OS and the remote workstation OS. -->

	Note: This guide assumes that your Linux distribution has Debian commands
	like `apt`.

	* A power supply of at least 24W to your host. The VIM3 can draw that much power when
	[DVFS](https://en.wikipedia.org/wiki/Dynamic_frequency_scaling) is enabled.

	* A working Fuchsia development environment on your host. In other words you
	should be able to build Fuchsia from its source code on your host. See
	[Build Fuchsia](#build).

	* A [USB to TTL serial cable](https://www.adafruit.com/product/954).

	* A USB-C to USB-\* cable that supports both data and power delivery.
	The USB-C side is for the VIM3. The other side can be whatever USB
	type your host supports.

	The following is optional:

	* A [heatsink](https://www.khadas.com/product-page/new-vim-heatsink).
	This enables running 2 CPU cores on the VIM3 at full speed without
	reaching 80°C, the critical temperature beyond which cores are throttled
	down.

	See the [VIM3 collection](https://www.khadas.com/shop?Collection=VIM3&sort=price_descending)
	in the Khadas shop for examples of compatible accessories.

	Note: All the links in this section are only for your convenience. You
	don't need to buy from these exact stores or these exact parts.

	## Build Fuchsia {#build}

	If you don't already have an [in-tree][glossary.in-tree] environment
	set up, you should start the process now because it can take a while to
	complete:

	1. [Download the Fuchsia source code](/docs/get-started/get_fuchsia_source.md).

	1. [Configure and build Fuchsia](/docs/get-started/build_fuchsia.md).

	* When building Fuchsia, use `fx set core.vim3` instead.

	Note: The rest of this guide assumes that your Fuchsia source code directory
	is located at `~/fuchsia`.

	Important: Whenever you see an `fx` command this guide assumes that your
	working directory is within your in-tree Fuchsia source code checkout.
	In other words this guide assumes that you run `cd ~/fuchsia` before
	running any `fx` commands.

	You'll use the Fuchsia development environment to build the Fuchsia image
	for VIM3 and run an in-tree CLI tool for flashing the Fuchsia image onto
	the VIM3.

	## Set up the hardware {#hardware}

	Set up the VIM3 to communicate with your host:

	1. Connect the VIM3 and your host to each other with the USB-C to USB-\* cable.
	The white LED on the VIM3 should turn on.

	Caution: Don't put a [USB hub](https://en.wikipedia.org/wiki/USB_hub)
	between the VIM3 and your host. The hub may make it harder for your
	VIM3 and host to detect and communicate with each other.

	This connection is used to power and flash the VIM3 with
	[`fastboot`](https://en.wikipedia.org/wiki/Fastboot).

	1. Connect the serial cable wires to the VIM3's GPIOs:

	* GND to pin 17.

	* RX (in to VIM3) to pin 18.

	* TX (out from VIM3) to pin 19.

	* Don't connect the power wire of your serial cable to any VIM3 GPIO.
	The VIM3 is getting power through the USB cable.

	Tip: Pins 1, 20, 21, and 40 are labeled on the circuit board.

	Caution: In general the colors for TX and RX wires are not standardized.
	For example your RX wire may be blue or green.

	See [Serial Debugging Tool](https://docs.khadas.com/products/sbc/vim3/development/setup-serial-tool)
	for an example image of how your serial wires should be connected to the VIM3.

	### Verify the serial connection {#serial}

	Make sure that you can view the logs being sent over the serial cable:

	1. Open Fuchsia's serial console:

	```posix-terminal
	fx serial
	```

	Note: If `fx serial` detects multiple USB devices and you don't know which one to use,
	try disconnecting the serial cable from your host, running `ls /dev/ttyUSB*`,
	then re-connecting the serial cable and running the command again. If you see
	no difference when running `ls /dev/ttyUSB` try `ls /dev/tty` or `ls /dev/*` instead.

	1. Press the reset button on the VIM3. The reset button is the one with the R
	printed next to it on the circuit board.
	See [VIM3/3L Hardware](https://docs.khadas.com/products/sbc/vim3/hardware/start) for
	a diagram. In your serial console you should see human-readable logs.

	## Erase the eMMC {#emmc}

	In later sections of this guide you'll update the bootloader and
	OS on the VIM3. These updates don't work unless you
	completely erase the eMMC first:

	1. Press the reset button on your VIM3.

	1. Right after you press the reset button, start repeatedly pressing the
	<kbd>Space</kbd> key as your VIM3 boots up. Make sure that your cursor
	is focused on your serial console. The bootloader process should pause
	and your serial console should show a `kvim3#` prompt. Your serial
	console is now providing you access to the U-Boot shell.

	1. Run the following command in the U-Boot shell:

	```posix-terminal
	store init 3
	```

	Your serial console logs should verify that the eMMC was correctly erased.

	See [Erase eMMC](https://docs.khadas.com/products/sbc/vim3/development/erase-emmc)
	for more details.

	## Update the Android image on the VIM3 {#android}

	<!-- Context: https://forum.khadas.com/t/unable-to-change-bootloader-for-vim3/12708/6 -->

	The Android image that ships by default on the VIM3 does
	not support Fuchsia installation. If you just received your VIM3
	from Khadas you must update your Android image:

	1. Click the following URL to download the updated Android image:
	<https://dl.khadas.com/firmware/vim3/android/VIM3_Pie_V210527.7z>

	1. Extract the compressed archive file (`VIM3_Pie_V210527.7z`).
	After the extraction you should have a `VIM3_Pie_V210527` directory
	with an `update.img` file in it.

	1. Follow the instructions in [Install OS into
	eMMC](https://docs.khadas.com/products/sbc/vim3/install-os/install-os-into-emmc-via-usb-tool).
	When running `aml-burn-tool` the value for the `-i` flag should be the
	path to your `update.img` file. Your command should look similar to this:

	```posix-terminal
	aml-burn-tool -b VIM3 -i ~/Downloads/VIM3_Pie_V210527/update.img
	```

	Caution: Make sure that you're following the instructions for Ubuntu
	and VIM3 by clicking the Install on Ubuntu and VIM3/VIM3L tabs.
	These instructions are not shown by default.

	Tip: The `TST Mode` workflow is probably the easiest and fastest way to get
	your VIM3 into Upgrade Mode.

	1. If the white and red LEDs on your VIM3 are off and the blue LED is on,
	it means that your VIM3 is in sleep mode. Try putting your VIM3
	back into [Upgrade Mode](https://docs.khadas.com/products/sbc/vim3/install-os/boot-into-upgrade-mode)
	and then pressing the reset button again.

	At this point the white LED on your VIM3 should be on and you should see
	logs in your serial console after you press the reset button on your VIM3.

	## Update the bootloader {#bootloader}

	Flash Fuchsia's custom bootloader onto the VIM3:

	1. Access the U-Boot shell again by pressing the reset button and
	then repeatedly pressing the <kbd>Space</kbd> key in your serial
	console. When your serial console shows the `kvim3#` prompt, you're
	in the U-Boot shell.

	1. In your U-Boot shell run the following command:

	```posix-terminal
	fastboot
	```

	You should see the following logs in your serial console:

	```
	g_dnl_register: g_dnl_driver.name = usb_dnl_fastboot

	USB RESET
	SPEED ENUM

	USB RESET
	SPEED ENUM
	```

	If you see the first line (`g_dnl_register: g_dnl_driver.name = usb_dnl_fastboot`)
	but not the lines after that, try using a different USB-C to USB-\* cable and make
	sure that it supports both data and power delivery.

	1. Open a new terminal window in your host and run the following commands:

	```posix-terminal
	cd ~/fuchsia/prebuilt/third_party/fastboot

	./fastboot flashing unlock

	./fastboot flashing unlock_critical

	./fastboot flash bootloader ~/fuchsia/prebuilt/third_party/firmware/vim3/u-boot.bin.unsigned

	./fastboot reboot
	```

	Caution: Installing the Android SDK Platform Tools probably installed another
	instance of `fastboot` on your host. When working with Fuchsia, remember to use
	the [in-tree][glossary.in-tree] version of `fastboot` at
	`~/fuchsia/prebuild/third_party/fastboot/fastboot`. The `fastboot` protocol allows arbitrary
	vendor protocol extensions and Fuchsia may rely on this functionality in the future.

	Note: You can also build the custom bootloader (`u-boot.bin.unsigned`) from source:
	<https://third-party-mirror.googlesource.com/u-boot/+/refs/heads/vim3>

	## Flash Fuchsia into the eMMC {#fuchsia}

	Complete these steps to install Fuchsia onto your VIM3 for the first time. You only
	need to do these steps once. Once you have Fuchsia running on your VIM3, the
	[Update your Fuchsia image](#update) workflow is a faster way to update the Fuchsia
	image on your VIM3.

	1. If you just ran the `./fastboot reboot` command from the last section then
	your VIM3 should already be in `fastboot` mode. You can check your `fx serial`
	logs to confirm. Otherwise press the reset button and then repeatedly press
	the <kbd>F</kbd> in your `fx serial` console until you see `USB RESET` and
	`SPEED ENUM` again.

	Important: You have to press the <kbd>F</kbd> key now to enter <code>fastboot</code>
	mode. Previously you pressed the <kbd>Space</kbd> key.

	1. From a separate terminal on your host run the following command:

	```posix-terminal
	fx flash
	```

	Your VIM3 is now running Fuchsia!

	## Update your Fuchsia image {#update}

	Complete these steps when you already have Fuchsia running on your VIM3
	and want to update the Fuchsia image on your VIM3.

	1. Run the following command from a terminal on your host:

	```posix-terminal
	fx serve
	```

	Leave this command running.

	1. Make some changes in your in-tree Fuchsia checkout and build the changes.

	1. Open a new terminal window and perform an OTA update of the Fuchsia image on your VIM3:

	```posix-terminal
	fx ota
	```

	## Appendix: Fix a bricked VIM3 {#bricks}

	Do these steps if you've [bricked](https://en.wikipedia.org/wiki/Brick_(electronics))
	your VIM3 and need to "factory reset" it:

	1. [Erase the eMMC](#emmc).
	1. [Update the Android image](#android).
	1. [Update the bootloader](#bootloader).
	1. [Flash Fuchsia into the eMMC](#fuchsia).

	## Appendix: Support {#support}

	* For issues that seem related to VIM3 hardware or firmware, try the
	[VIM3 official docs](https://docs.khadas.com/linux/vim3/index.html) and
	[Khadas VIM3 official forum](https://forum.khadas.com/c/khadas-vim3/30).
	* For issues that seem related to Fuchsia, try the
	[Fuchsia mailing lists and chat rooms](/docs/contribute/community/mailing-lists.md).

	## Appendix: Feature support {#features}

	Fuchsia currently supports these features of the VIM3:

	* UART Serial Debugger
	* Paving over ethernet and USB
	* Storage (eMMC)
	* HDMI Display and Framebuffer
	* GPU (Mali) and Vulkan graphics
	* Ethernet
	* SDIO
	* I2C
	* GPIO
	* Temperature Sensors and DVFS
	* RTC
	* Clock
	* Fan
	* NNA
	* USB-C in peripheral mode
	* USB-A

	These features are under development and may not be supported:

	* Video decoder
	* SPI
	* Audio

	The following features are not supported, but might be added by future
	contributions:

	* SPI Flash
	* USB-C in host mode
	* Power management and PMIC
	* Wake on LAN
	* UART BT

	These features are not supported and are unlikely to be added:

	* Video encoding (due to non-public firmware)
	* Trusted Execution Environment / secure boot

	## Appendix: Update the boot splash screen {#splash}

	To update the boot splash screen to be the Fuchsia logo, run the following command
	from a host terminal while the VIM3 is in `fastboot` mode:

	```posix-terminal
	fastboot flash logo ~/fuchsia/zircon/kernel/target/arm64/board/vim3/firmware/logo.img
	```