HDMI on Snickerdoodle

Copyright (c) 2020-2021 Antmicro

This is an example design for the open hardware Snickerdoodle HDMI breakout board. The design utilizes the following IP cores:

• FastVDMA
• HDMI Transmitter
• AXI Display Controller
• LiteX Mixed-mode Clock Manager

This setup is designed to work with a Linux system with a /dev/fb0 framebuffer device that outputs its contents via the HDMI connector of the breakout board.

Building the FPGA design

1. Setup the Vivado environment:

   source /path/to/Vivado/2018.3/settings64.sh
   

2. Use FuseSoC to build the bitstream:

   fusesoc --cores-root cores --cores-root src run snickerdoodle_hdmi
   

   FuseSoC will try to program the FPGA. Note that if the device is not connected properly, the command will fail.

   The bitstream will be stored here:

   build/snickerdoodle_hdmi_0/default-vivado/snickerdoodle_hdmi_0.bit
   

3. Generate the FSBL from Vivado design

Building the software

1. Clone and build the U-Boot bootloader:

   git clone https://github.com/krtkl/snickerdoodle-u-boot.git
   pushd snickerdoodle-u-boot
   make snickerdoodle_black_defconfig
   make CROSS_COMPILE=arm-linux-gnueabihf-
   ln -s u-boot u-boot.elf
   popd
   

   The resulting u-boot.elf file will be located in the snickerdoodle-u-boot directory.

2. Clone and build the Linux kernel:

   git clone https://github.com/antmicro/linux-xlnx.git -b axi_dispctrl
   pushd linux-xlnx
   make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- LOADADDR=0x8000 snickerdoodle_defconfig
   make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- LOADADDR=0x8000 -j$(nproc)
   make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- LOADADDR=0x8000 uImage
   popd
   

   The resulting uImage file will be located in the linux-xlnx/arch/arm/boot/ directory.

3. Clone devicetree repository and build the dtb file:

   git clone https://github.com/antmicro/snickerdoodle-dts.git -b hdmi-support
   pushd snickerdoodle-dts
   make
   popd
   

   The resulting snickerdoodle-black.dtb file will be located in the snickerdoodle-dts directory.

4. Create a boot.bif file with the following contents:

   the_ROM_image:
   {
       [bootloader]/path/to/fsbl.elf
       /path/to/snickerdoodle_hdmi_0.bit
       /path/to/u-boot.elf
   }
   

5. Generate a boot.bin file (You can use the mkbootimage tool or Xilinx SDK):

   To generate the boot.bin file with mkbootimage run:

   mkbootimage boot.bif boot.bin
   

Once all the binaries are ready, prepare an SD card following the official guide and replace the Linux kernel, devicetree and boot.bin files with the ones generated in the steps above. Insert the SD card to the snickerdoodle board and boot the system.

Running Linux Desktop Environment

1. Power up the board and connect to the serial console

2. Attach an HDMI display to the board (by default it should show a black screen at 1080P60 resolution)

3. Log in an check if the wireless connection is up with ip a

4. Install required packages on the device:

   sudo apt update
   sudo apt install xfce4 x11vnc
   

5. Create the /usr/share/X11/xorg.conf.d/10-fbdev.conf file with the following contents:

   Section "Device"
           Identifier "axi_dispctrl FB"
           Driver "fbdev"
           Option "fbdev" "/dev/fb0"
   EndSection
   

6. Start XFCE:

   sudo rm /dev/dri/card0
   sudo startxfce4
   

   You should now see an XFCE session on the HDMI output.

7. Snickerdoodle and breakyBreaky have no USB Host ports which could be used to connect keyboard and mouse. A VNC server can be used to forward HID devices from a PC to the device. To do it connect to the board using SSH and start a VNC server with:

   x11vnc -display :0
   

   Once the server is running you can connect to it using any VNC client.