2017.12.15 : Black Mesa Labs is proud to present two open-source-hardware DVI video boards for adding TMDS digital video to FPGA platforms with standard PMOD connectors. These two boards are currently available to purchase as bare fabs directly from OSH-Park, or Gerbers and design files may be downloaded from BML here.
BML 3bit DVI over single-PMOD:
The BML 3bit DVI over single-PMOD uses 7 of 8 available LVCMOS 3.3 pins on a single PMOD to provide 3bit color ( R,G,B 100% On or Off ). Example Verilog design drives 800×600 using a 40 MHz dot clock. The TI TFP410 is very versatile in the resolutions it can generate and is really just limited by the clock that the FPGA can provide and the data rates the PMOD connectors are capable of. The bare 2-layer fab may be purchased from OSH-Park directly for $5 USD ( for 3 boards ) from this link. The TFP410 is about $8 USD. The IC and this HDMI Connector is pretty much the BOM, so the entire cost to assemble is less than $20 USD. The rest of the BOM is Qty-2 0603 0.1uF Caps ( 25V 20% X7Rs were used ), Qty-1 0603 10uF Cap, Qty-1 0805 500ohm 1% resistor and an optional 0805 Ferrite Bead ( 240-2390-1-ND was used, but may be replaced with a wire ). If you don’t want to power the TFP410 from your FPGA’s 3V rail, the Ferrite Bead may be removed and a BU33 ( or equivalent 5SSOP) 3.3V LDO regulator and 10uF cap may be stuffed and the board may be powered by a 5V input via.
The 3bit color Test Pattern from the board driven by FPGA sample design looks like this:
Note that blue exists, it is just off screen. With 3bits of color you get 8 colors by additive color mixing for Black, White, Red, Green, Blue, Yellow, Cyan, Magenta.
Below is a picture of the 3b board plugged into a Lattice ICE40 icoBoard which is available from Trenz here. The smaller iceZero board (PiZero dimensions), also a Lattice ICE40 is a joint BML and Trenz design and would also be a good platform for DVI video and is available here.
Design files for the board, including Gerbers, BOM and text netlist description may be downloaded from my public Dropbox here.
BML 12bit DVI over dual-PMOD:
The BML 12bit DVI over dual-PMOD uses 16 of 16 available LVCMOS 3.3 pins on two PMODs spaced 0.900″ center-to-center per Digilent spec. The 12bit color provides 16 shades each for Red, Green and Blue. Example Verilog design drives 800×600 using a 40 MHz dot clock. The bare 2-layer fab may be purchased from OSH-Park directly for $11 USD ( for 3 boards ) from this link. BOM is identical to the 3b version, just another PMOD 2×6 right-angle 0.100″ female connector is added. Test Pattern video from the board looks like this ( blue is off screen ):
Example Verilog. The open-source example Verilog here was used to generate the test patterns shown from a Xilinx Spartan3 board. The design itself is very portable and only requires the FPGA to have a 40 MHz clock and the ability to mirror the clock out to the TFP410 IC using a ODDR or equivalent DDR clock mirroring and the IO ring. If IO timing for your particular FPGA board doesn’t work, often it may be tweaked to work by adjusting the drive strength and slew rates of the clock out relative to the data out. Note: BML deliberately chose NOT to use the built-in DDR capability of the TFP410 due to wide variability of I/O timing from various FPGA boards over PMOD interfaces. SDR is most likely to work across platforms so it was chosen.
A word about video timing – it is tricky. The TFP410 will generate just about any timing you throw at it, but your monitor ( or TV ) might not like it. This on-line calculator is extremely helpful in calculating all the Sync Widths, Front Porch, Back Porch timing parameters. Provided with a resolution ( 800×600 for example ) it will spit out the Verilog def_h_total and def_v_total times ( 1000×667 at 40 MHz for 60 Hz for example ) and the blanking times ( Hsync and Vsync widths, 56 and 3 for example for def_h_sync, def_v_sync ). The porch numbers are then whatever is left over. For example 1000-800-56 = 144. 144/2 = 72 which should work for def_h_fp ( Front Porch ) and def_h_bp ( Back Porch ). It takes patience and experimentation to generate something your monitor is happy with. If your display locks, but isn’t centered, then your porch numbers need to be adjusted accordingly.
BML hopes that you enjoy these free and open-source board designs for adding DVI video to FPGAs. Check back soon for posting on new USB 3.0 to PMOD adapter using FTDI FT600 FIFO Chip.
2017.12.19 : Updated to fix Gerbers for 3b version with incorrect soldermask on video connector.