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Chamelium automates external display testing across VGA, HDMI, and DisplayPort (DP), helping to identify graphics bugs and regressions in a reliable and scalable way. It can emulate user behavior across a wide range of scenarios, such as plugging in (or unplugging) an external monitor before or after suspending, waking, or rebooting a device. It also allows us to simulate all types of displays on the market, at various resolutions and refresh rates, including non-standard or flaky behavior.

Chamelium is the public name of the internal Google project Chameleon (similar to Chromium and Chrome). You may see references to the original codename throughout the documentation linked below.

Chamelium consists of 3 primary components:

a hardware board which acts as an external display emulator, simulating
output over VGA, HDMI, and DP. You can either ask a hardware manufacturer to
build these for you, or contact
to request a few units.

an off-the-shelf FPGA board (SoCKit) to capture the output frames, with a
micro-SD card that provides the Linux image and FPGA configuration. This can
be purchased from distributors like

source code for the underlying test infrastructure and logic

Please direct any questions about Chamelium to

Setting up Chamelium


(Block diagram)


(Front side of the external display emulator board. On the left side there is one HDMI, two DP, and one VGA connector. On the right side there is the HSMC connector.)


(Back side of the external display emulator board)

You will need the following equipment to set up all the individual components in Chamelium:

1 external display emulator board (described above)

1 FPGA board (described above). Included in the box should be:

    1 ethernet cable

    1 power adapter

    1 mini-USB to USB-A cable

1 micro-SD card with at least 1GB of storage

1 micro-SD card reader

[1 HSMC flex

Depending on what you’d like to test, one of each of the following cables:

1 Linux host (workstation or laptop)

1 USB drive with at least 4GB of storage

The following equipment is optional:

4 [M3 screws](
(6mm in length)

2 washers

4 M3 nuts (15mm in length)

4 M3 nuts (6mm in length)

1 additional VGA cable and 1 external monitor for debugging, if you’d like
to see the display output as well

Configure the FPGA board

Set the jumpers on the top side of the board

    J15 = down

    J16 = down

    J17 = up

    J18 = up

    J19 = down

    JP2 - 2.5V <img alt="image"
    src="s2mbf9hZBTGKMFHBgqQqDiA.png"> <img
    src="sjR3S5TzIrNaCyuUbwvWwbA.png"> <img

Set the jumpers on the bottom side of the board

    MSEL = up-up-down-up-up-up = uncompressed RBF (001000) <img alt="image"

Image the SD card

Download and unzip it. dd tio_v3.img onto the micro-SD card from your Linux host.

sudo dd if=tio_v3.img of=/dev/sdx bs=4M oflag=sync

(Replace the above /dev/sdx to a proper path, like /dev/sdc, by checking the SD device)

Now insert the micro-SD card into the FPGA board.

v3 image:

v2 image (old):

Increased user space from 20M to 4G.

Updated glibc from 2.15 to 2.29.

Fixed broken pip.

v1 image (old): tio.image.gz

Configure the external display emulator board

First, attach the HSMC flex cable to connect the two boards.

Optionally, if you’d like a more compact setup, you can stack the FPGA on top of the external display emulator board and secure them into place per the diagram below:


Note that the longer nuts should be placed in between the two boards, with the shorter nuts on the bottom.

Attach all cables

Attach the power and HDMI, DP, and/or VGA cables (depending on what
interface you’d like to test), per the diagram below.

Connect the other end of the HDMI, DP, and/or VGA cable to the device under
test (DUT) - the device you’d like to run the tests against.

Then connect the mini-USB port in the diagram below to your Linux host.

The additional VGA port next to the ethernet port is optional (it’s for
debugging purposes only) and should be connected to an external monitor if
you decide to use it. <img alt="image"

Next, connect the ethernet port on the FPGA to the same network as your
Linux host and as your DUT.

Running the tests

Verify your network setup

Power on the FPGA board by pressing the red button. This will boot from the
SD card.

Connect to the board via UART

sudo minicom -D /dev/ttyUSB0 -o -w -s

Select Serial port setup

Set the terminal to be 115200 8N1, and the Hardware Flow Control to No

Select Save setup as dfl to save these changes as the default

Restart the FPGA board

Once the FPGA is done booting, login as root

Make sure you can ping the FPGA board from your Linux host, and the Linux
host from your FPGA. You may need to setup a DHCP server on your Linux host.

Switch your DUT into developer mode

Finally, make sure you can ping the DUT from your Linux host.

The IP address will change at each reboot, as the MAC address of the board is not fixed. You can fix it by running the following commands in uboot (change XX to hex numbers of your choice):

> setenv ethaddr 0A:XX:XX:XX:XX:XX

> saveenv

> boot

Setup your Linux host, DUT and the FPGA

[Checkout the source
tree]( for Chromium OS

[Create and enter a
via the command cros_sdk

Build the packages and images to run the tests

export BOARD=[name of your DUT’s board, viewable at chrome://version]

cros build-packages --board=$BOARD

[Install Chromium OS onto your

    Connect your USB drive to your Linux host

    Build a test image

cros build-image --board=$BOARD test

    Run the command displayed in the output in the terminal, under the
    section, “To copy the image to a USB key, use…”

cros flash usb:// ../build/images/[...]/chromiumos_test_image.bin

    Now, boot your DUT from the USB drive (with the test image) - you’ll
    need to [enter
    login as root, and run enable_dev_usb_boot. Then, connect your USB drive
    to your DUT and restart - you’ll need to enter \[Ctrl\]-\[u\] at the
    developer mode boot screen.

    After the DUT has booted, switch to vt2, login as root (the password on
    the test image is test0000) and run chromeos-install .


    Shutdown the DUT, disconnect the USB drive, and then turn on the DUT.

On your Linux host, setup the ARM toolchain and set the relevant environment

cd ~/trunk/src/scripts

./setup_board --board arm-generic

export CHAMELIUM_IP=[IP address of the FPGA board]

export DUT_IP=[IP address of the DUT]

Make and deploy chameleond on the FPGA

cd ~/trunk/src/platform/chameleon


make remote-install CHAMELEON_HOST=$CHAMELIUM_IP

Setup root password and SSH key


ssh root@$CHAMELEON_IP mkdir -p .ssh

cat ~/trunk/chromite/ssh_keys/ | ssh root@$CHAMELEON_IP 'cat

>> .ssh/authorized_keys'


Run the tests

Set $TEST_NAME to any of the following. Please note that the starred test
items (\*) require [servo](/chromium-os/servo), and will fail without it.


























export TEST_NAME=[name of the test you’d like to run]

Alternatively, you can run an entire test suite by setting $TEST_NAME to
either of these values, below. Each suite consists of a combination of the
individual tests listed above.



Run a test [using

cd ~/trunk/src/scripts

test_that --board=$BOARD --args "chameleon_host=$CHAMELIUM_IP" $DUT_IP


Advanced usage

For additional instructions on how to modify tests or the FPGA image, please refer to the documentation below.

The hardware specs include:

    Schematics (see attachment: Chameleon-B1_R1.2_Release \[for external

    Board file (see attachment: Chameleon_B1_R1.2_Release.brd)

    HDMI receiver (see attachments: IT6803TE Datasheet_for_Google v0.83.pdf
    and IT6803 Programming Guide.1.05.pdf)

    DP receiver (see attachments: IT6506_Datasheet_for_Google_v1.3.pdf and
    IT6506 Programming Guide.pdf)

    VGA receiver (see attachments: cat9883c_datasheet_for_Google_Rev1 3.pdf
    and CAT9883CRegisterRev01.pdf)

    [Chamelium Hardware Design

    [Chamelium External Display

    [HSMC pin

    [FPGA pin

    FPGA pin locations (see attachment: FPGA pins.png)

    [HSMC spec](