Finally HDMI

A project log for HDMI to LVDS panel converter

Convert HDMI out from Rasperry Pi to scrapped LVDS panel with FPGA board

JulienJulien 08/31/2016 at 17:160 Comments

LVDS input is operational, the last step is to process hdmi output

The good news is that DVI and LCD signal protocol are very similar : pixel, hsync, vsync and clock. The main difference is the electrical signal, LCD uses LVDS and DVI uses TMDS, they are both differencial but incompatible.

Xilinx Spartan chips are able to natively manage these two types of electrical signal which will highly simplify the requirement. Xilinx exposes a DVI in/out verilog implementation in an application note, thats great since I just needed to create an interface between the LVDS controller previously used and the DVI input example.

To test, I switched to minispartan6 which has an HDMI input connector. The design does not change very much, both spartan 3 and 6 manage LVDS and TMDS, I only modified the pins connections for LVDS.

Both verilog controllers manage the serialization/deserialization of the two signals and expose the resulting red/green/blue/vsync/hsync signals.

It is actually that simple, connect rgb, sync and clock between the two controllers !

There is just a small problem, DVI output 24bits color and the panel takes 18bits but a truncation seems sufficient.