Since past few weeks, I’ve been trying to put my Mimo UM-740 touchscreen monitor to a good use. Sounds old school, but yeah we are talking about pre-ipad age when I used it as a touch screen skypephone device.
Follow this tutorial to configure the monitor as a primary display for raspberry-pi. Although I have explained the steps against Nanovision Mimo UM740, they should work with any displaylink USB monitor.
- 7 port powered USB hub
- RaspberryPi running raspbian wheezy
- Mimo UM740 touchscreen monitor
- Ubuntu 12.04 machine for kernel compilation
Step 1: Prepare SD card
- Setup SD card with raspbian wheezy
- Boot using a standard hdml monitor
- Using raspi-config, enable ssh server and disable the GUI mode on startup. This will enable us to work on it without a monitor.
Step 2: Compile Kernel with udlfb support
First, we need to enable Displaylink framebuffer support in the kernel. I have followed these steps to compile the kernel on Ubuntu 12.04.
2.1: Install dependencies
apt-get install git-core gcc-4.6-arm-linux-gnueabi
2.2: Symlink the cross compiler
sudo ln -s /usr/bin/arm-linux-gnueabi-gcc-4.6 /usr/bin/arm-linux-gnueabi-gcc
2.3: Checkout source code
mkdir raspberrypi cd raspberrypi git clone git://github.com/raspberrypi/linux.git
cd linux cp arch/arm/configs/bcmrpi_cutdown_defconfig .config make ARCH=arm CROSS_COMPILE=/usr/bin/arm-linux-gnueabi- oldconfig #optional#make ARCH=arm CROSS_COMPILE=/usr/bin/arm-linux-gnueabi- menuconfig
Make sure that displaylink framebuffer support is enabled:
Follow ‘Device Drivers’ > ‘Graphics Support’ > ‘Support for Framebuffer support’.
Enable ‘Displaylink USB Framebuffer support’ by selecting ‘M’.
make ARCH=arm CROSS_COMPILE=/usr/bin/arm-linux-gnueabi- -k -j3
Step 3: Replace kernel.img on SD card
Once compilation is successful, package the kernel image:
mkdir ../modules make modules_install ARCH=arm CROSS_COMPILE=/usr/bin/arm-linux-gnueabi- INSTALL_MOD_PATH=../modules/ cd ../tools/mkimage/ ./imagetool-uncompressed.py ../../linux/arch/arm/boot/Image
This will create kernel.img in the current directory. Mount the SD card and replace existing kernel.img with the one which we just built.
Connect the monitor through a powered USB hub and reboot the pi. If everything has gone well, you should see a green screen.
Connect to ethernet & check if monitor was detected correctly:
$ dmesg | grep DisplayLink usb 1-188.8.131.52: Manufacturer: DisplayLink udlfb: DisplayLink nanovision MiMo - serial #USM700-8B280858 udlfb: DisplayLink USB device /dev/fb1 attached. 800x480 resolution. Using 1504K framebuffer memory
You should see two framebuffer devices, one for the hdmi adapter (fb0) and other for the USB monitor (fb1).
$ ls /dev | grep fb fb0 fb1
Step 4: Configure Xorg
Using ssh, create /etc/X11/xorg.conf on the pi using following configuration:
Section "Device" Identifier "uga" driver "fbdev" Option "fbdev" "/dev/fb1" Option "ShadowFB" "off" EndSection Section "Monitor" Identifier "monitor" EndSection Section "Screen" Identifier "screen" Device "uga" Monitor "monitor" EndSection Section "ServerLayout" Identifier "default" Screen 0 "screen" 0 0 EndSection
Start the GUI mode using ‘startx’ and you are done!