fpga-graphics

Beginning FPGA Graphics

This folder accompanies the Project F blog post: Beginning FPGA Graphics. These SystemVerilog designs introduce you to displays and demonstrate how to draw your first FPGA graphics. You can freely build on these MIT licensed designs. Have fun.

File layout:

• ecp5 - designs for ULX3S and other ECP5 boards
• ice40 - designs for iCEBreaker and other Lattice iCE40 boards
• sim - simulation with Verilator and LibSDL; see the Simulation README
• xc7 - designs for Arty and other Xilinx 7 Series boards with VGA output
• xc7-dvi - designs for Nexys Video and other Xilinx 7 Series boards with DVI output

These designs make use of modules from the Project F library.

Demos

• Square
• Flag of Ethiopia
• Flag of Sweden
• Colour

Learn more about the designs and demos from Beginning FPGA Graphics, or read on for build instructions.

Traditional flag of Ethiopia running as a Verilator simulation.

ULX3S Build

I have tested these designs with recent (early 2024) versions of Yosys and nextpnr. You can get pre-built binaries for Linux, Mac, and Windows from YosysHQ OSS CAD Suite.

Once the tools are installed, it's straightforward to build the designs.

For example, to build square; clone the projf-explore git repo, check the correct FPGA model is set near the top of projf-explore/graphics/fpga-graphics/ecp5/Makefile then:

cd projf-explore/graphics/fpga-graphics/ecp5
make square

After the build completes, you'll have a bit file, such as square.bit. Use the bit file to program your board:

openFPGALoader --board=ulx3s square.bit

If you get the error JTAG init failed with: unable to open ftdi device, try running openFPGALoader with sudo.

NB. ULX3S support was added in February 2024 and likely has some rough edges.

iCEBreaker Build

You can build projects for iCEBreaker using the included Makefile with Yosys, nextpnr, and IceStorm Tools.

You can get pre-built binaries for Linux, Mac, and Windows from YosysHQ OSS CAD Suite.

Once the tools are installed, it's straightforward to build the designs.

For example, to build flag_ethiopia; clone the projf-explore git repo, then:

cd projf-explore/graphics/fpga-graphics/ice40
make flag_ethiopia

After the build completes, you'll have a bin file, such as flag_ethiopia.bin. Use the bin file to program your board:

iceprog flag_ethiopia.bin

If you get the error Can't find iCE FTDI USB device, try running iceprog with sudo.

Tested Versions

The iCE40 designs have been tested with:

• OSS CAD Suite 2023-03-01

Arty Build

To create a Vivado project for the Digilent Arty (original or A7-35T); clone the projf-explore git repo, then start Vivado and run the following in the Tcl console:

cd projf-explore/graphics/fpga-graphics/xc7/vivado
source ./create_project.tcl

You can then build the designs as you would for any Vivado project.

Tested Versions

The Arty designs have been tested with:

• Vivado 2022.2

Behavioural Simulation

This design includes test benches for the clock_480p and simple_480p modules. You can run the test bench simulations from the GUI under the "Flow" menu or from the Tcl Console with:

launch_simulation
run all

By default, the simple_480p test bench is run, but you can switch to the clock_tb test bench using the GUI or from the Tcl console:

set fs_sim_obj [get_filesets sim_1]
set_property -name "top" -value "clock_tb" -objects $fs_sim_obj
relaunch_sim
run all

Other Xilinx 7 Series Boards

It's straightforward to adapt the project for other Xilinx 7 Series boards:

1. Create a suitable constraints file named <board>.xdc within the xc7 directory
2. Make a note of your board's FPGA part, such as xc7a35ticsg324-1L
3. Set the board and part names in Tcl, then source the create project script:

set board_name <board>
set fpga_part <fpga-part>
cd projf-explore/graphics/fpga-graphics/xc7/vivado
source ./create_project.tcl

Replace <board> and <fpga-part> with the actual board and part names.

Nexys Video Build

To create a Vivado project for the Digilent Nexys Video; clone the projf-explore git repo, then start Vivado and run the following in the Tcl console:

cd projf-explore/graphics/fpga-graphics/xc7-dvi/vivado
source ./create_project.tcl

You can then build the designs as you would for any Vivado project.

Tested Versions

The Nexys Video designs have been tested with:

• Vivado 2022.2

Verilator SDL Simulation

You can simulate these designs on your computer using Verilator and SDL. The Simulation README has build instructions.

Linting

If you have Verilator installed, you can run the linting shell script lint.sh to check the designs:

$ ./fpga-graphics/lint.sh
## Linting top modules in ./sim
##   Checking ./sim/top_colour.sv
##   Checking ./sim/top_flag_ethiopia.sv
##   Checking ./sim/top_flag_sweden.sv
##   Checking ./sim/top_square.sv
## Linting top modules in ./ice40
##   Checking ./ice40/top_colour.sv
##   Checking ./ice40/top_flag_ethiopia.sv
##   Checking ./ice40/top_flag_sweden.sv
##   Checking ./ice40/top_square.sv
## Linting top modules in ./xc7
##   Checking ./xc7/top_colour.sv
##   Checking ./xc7/top_flag_ethiopia.sv
##   Checking ./xc7/top_flag_sweden.sv
##   Checking ./xc7/top_square.sv
## Linting top modules in ./xc7-dvi
##   Checking ./xc7-dvi/top_colour.sv
##   Checking ./xc7-dvi/top_flag_ethiopia.sv
##   Checking ./xc7-dvi/top_flag_sweden.sv
##   Checking ./xc7-dvi/top_square.sv

You can learn more about this from Verilog Lint with Verilator.

SystemVerilog?

These designs use a little SystemVerilog to make Verilog more pleasant. See the Library README for details of SV features used.