Minimal DVI / HDMI Framebuffer

Github: https://github.com/ultraembedded/core_dvi_framebuffer

This component allows the addition of a DVI/HDMI output to your FPGA project.
The IP fetches pixel data from an external AXI-4 memory target and converts to a TMDS suitable for driving DVI or HDMI (DVI mode) outputs from a FPGA.

Based around Mike Field's TMDS encoder code.

Features

• HDMI / DVI TMDS output.
• RGB565 input format.
• AXI-4 bus master with burst support.
• 4KB pixel data prefetch FIFO (which map to BlockRAMs in Xilinx FPGAs).
• AXI-4 Lite register interface with programmable framebuffer fetch address, enable, interrupt control.
• Start of frame interrupt output.
• Configurable display resolution (640x480, 800x600, 1280x720, 1920x1080).
• Works with the Linux 'simple-framebuffer' driver.

Interfaces

Name	Description
clk_i	Clock input - must be suitable for the configured res/refresh rate.
clk_x5_i	Clock input x 5.
rst_i	Async reset, active-high.
cfg_*	AXI-4 Lite configuration port (optional if VIDEO_ENABLE=1).
outport_*	AXI4 master interface for pixel fetch data.
intr_o	Active high interrupt output (single cycle strobe).

Params

Name	Default	Description
VIDEO_WIDTH	800	Display resolution (H).
VIDEO_HEIGHT	600	Display resolution (V).
VIDEO_REFRESH	72	Display refresh rate.
VIDEO_ENABLE	1	Pixel fetch enable after reset (changeable via AXI-4L regif).
VIDEO_FB_RAM	32'h3000000	Framebuffer base address (changeable via AXI-4L regif).

Linux Framebuffer

Example Linux DTS configuration with the framebuffer located @ 0x300_0000 and 800x600 display resolution;

    framebuffer {
      compatible = "simple-framebuffer";
      reg = <0x3000000 (800 * 600 * 2)>;
      width = <800>;
      height = <600>;
      stride = <(800 * 2)>;
      format = "r5g6b5";
    }; 

Testing

Tested on a Xilinx Artix 7 (Digilent Arty A7) with Dell U2515 monitor and a LG LCD TV with various resolutions. Used with the Linux Kernel 'simple-framebuffer' driver.

References

• TMDS Encoding
• DVI Interface