Frequently Asked Questions

How much power does the HDMI-Display need?

Depending on the display and backlight current between 400 to 1000mA. For the Raspberry Pi we recommend at least a 5V 2A power supply. If you have problems like a flickering screen, then check your USB cables. Some cables have very thin wires and so there is a voltage drop >0.5V on the cable.

What boards/computers are compatible with the HDMI-Display?

In general all boards/computers with a HDMI output can drive the display and the respective settings are loaded from the EDID EEPROM (empty on new adapters) automatically. If there are any problems, then the settings can be made manually. For example the Raspberry Pi ignores no standard display timings. Infos about setting the display timings can be found here: Raspberry Pi, BeagleBone, CubieBoard, ODROID, UDOO

The touchpanel acts as USB HID mouse with absolute coordinates. So you do not need a special driver. An inversion/rotation of the coordinates can be done via the serial interface command ATS6.

What displays are compatible with HDMI to RGB Adapter board?

All displays with the standard 40 pin connector (parallel RGB interface) are compatible. If the display has a touchpanel please make sure the jumpers are in the right position and the correct firmware is on the ATmega32u4 microcontroller, before connecting the screen. Here is a Displays Compatibility List with further infos and the jumper settings can be found in the schematics PDF file.

Hints about Displays

Further infos (e.g. ghost images) about displays can be found here.

How to change the console font?

The font can be changed with console-setup or edit the file /etc/default/console-setup.

$ sudo dpkg-reconfigure console-setup
Encoding to use on the console: <UTF-8>
Character set to support: <Guess optimal character set>
Font for the console: Terminus (default is VGA)
Font size: 6x12 (framebuffer only)

How to emulate a right mouse button under X-Window-System?

  • Debian Wheezy

    Open evdev.conf

    $ nano /etc/X11/xorg.conf.d/evdev.conf
    

    and add the following section:

    Section "InputClass"
        Identifier "Touchscreen"
        MatchProduct "ATmega32u4 USB IO Board"
        Driver "evdev"
        Option "EmulateThirdButton" "1"
        Option "EmulateThirdButtonButton" "3"
        Option "EmulateThirdButtonTimeout" "1000"
        Option "EmulateThirdButtonMoveThreshold" "30"
    EndSection
    
  • Debian Jessie

    The EmulateThirdButton option has be removed from Jessie and as workaround twofing can be used: Installation Guide, Source Code

Where can I found an on-screen keyboard?

You can install Florence Virtual Keyboard or Matchbox Virtual Keyboard with the following commands:

sudo apt-get install florence
sudo apt-get install matchbox-keyboard

Does Qt evdevtouch is working with the touchpanel/mouse?

The Qt plugin evdevtouch is not working with the touchpanel, please use tslib.

Why is the touchpanel/mouse not working under Kodi/XBMC?

Kodi needs access to the input devices and this can be done by creating the following rule. The mouse device also has to use screen coordinates: (serial command ATS6=8).

Open/create 99-input.rules

$ nano /etc/udev/rules.d/99-input.rules:

and add the following rules:

SUBSYSTEM=="input", GROUP="input", MODE="0660"
KERNEL=="tty[0-9]*", GROUP="tty", MODE="0660"

If there are problems with the display output, then add the line hdmi_drive=1 to /boot/config.txt.

How to switch off and on the HDMI output on the Raspberry Pi?

When using displays with onboard backlight boost regulators the backlight can be switched off when the HDMI output is deactivated. If you get a wrong image, when you power on the HDMI output then add the line hdmi_drive=1 to the file /boot/config.txt.

  • HDMI off

    $ tvservice -o
    
  • HDMI on

    $ tvservice -p
    $ fbset -depth 8
    $ fbset -depth 16
    $ xrefresh
    

How to flash/update the EDID EEPROM?

The EEPROM (I2C) is empty on new adapters and can be flashed via the ATmega32u4 Microcontroller. The jumper/switch settings can be found in the schematics PDF file. and the programming can be done via the firmware (see EDID EEPROM Programming). To modify the EDID data under a Windows OS you can use Raylar’s Phoenix EDID Designer.