vhdl-hdmi-out

HDMI Out driver written in VHDL for 7-Series Xilinx FPGAs. Only video side is implemented and audio stuff is not included. Three resolutions are added. Serial cock runs at 5x the pixel clock and uses OSERDES blocks to generate the TMDS signals. Can be used to connect to a DVI input as well since they share the same protocol and timings. A SERIES6 generic is added to replace OSERDES2 blocks with OSERDES1 blocks that are used in 6-Series. Since OSERDES1 is not encrypted, GHDL can also elaborate and simulate the behavior.

Project is configured to run at 125 Mhz clock, but can be configurable from the clock_gen.vhd to run at different frequencies. timing_generator.vhd generates the the video timing signals: hsync, vsync, video_active as well as the pixel x and y locations. pattern_generator.vhd and objectbuffer.vhd are used to generate RGB pixel values and rgb2tmds.vhd is the top module that handles the conversion from RGB values to TMDS signal outputs.

GHDL can be used to simulate the circuit, and GTKWave can be used to display the waveform. makefile is given to automate elaboration steps. It needs Xilinx Vivado installation to compile Xilinx supplied primitives such as BUFG, OBUFDS and PLLE2. However, OSERDES2 that is used in the project is encrypted and cannot be imported to GHDL, so a generic is added to replace it with OSERDES1 that is used in 6-Series devices. It is enabled by default in the simulation, and should be disabled if OSERDES2 blocks are to be used. Update the relevant line with your Xilinx Vivado installation. (or run with XILINX_VIVADO environmental variable instead)

Files

+- rtl/
| -- hdmi_out.vhd          : hdmi out top module
| -- clock_gen.vhd         : generates pixel (1x) and serial (5x) clocks
| -- timing_generator.vhd  : generates timing signals for a given resolution
| -- rgb2tmds.vhd          : rgb to tmds parent module
| -- tmds_encoder.vhd      : 8b/10b rgb to tmds encoder
| -- serializer.vhd        : 10b tmds signal serializer to be sent out using serial (5x) clock
| -- objectbuffer.vhd      : rgb object generator based on active area
| -- pattern_generator.vhd : rgb color spectrum pattern generator based on active area
+- sim/
| -- tb_hdmi_out.vhd       : testbench for hdmi out module
+- imp/
| -- arty-z7.xdc           : constraints for Arty-Z7 / Pynq-Z1 boards

Features

• Supports 720p (1280x720), SVGA (800x600), and VGA (640x480) modes.
• Two patterns are included that are selectable on synthesizing
  • a rainbow color pattern - shows color spectrum
  • an object buffer for a game base - generates a wall, a box, and a ball. Wall is the stationary object, and box / ball are movable objects using the position signals. Background color can also be changed from top level
• Tested on Arty-Z7-20, Pynq-Z1 and Pynq-Z2 boards.

Misc.

• There is an on/off problem on Pynq-Z2 board when the clock is sourced from 125 Mhz PL clock. The display turns on for ~1 seconds and off for ~1 second. This problem goes away when the clock is generated from ZYNQ IO PLL.
  • Yuri Cauwerts kindly pointed out that connecting Ethernet cable fixes the problem.
• tmds_encoder usually needs pipelining for fixing timing problems. Usually I leave this to students to figure out how to implement it.
• vhdl-display-simulator can be used to see the screen output without implementing your designs.