The repository contains the implementation of the Brus-16 educational game console.

Gameplay videos:

• Architecture.
• Board-specific.
• Build firmware for new game.
• PMOD joystick kit connection.
• Simulation.
• Tests.

More general information can be found here.

High-level diagram of a game console:

CPU:

• The Single-cycle processor calculates the next frame and enters the wait state.
• After the resume signal, it continues its work from the previous location.
• ISA is available here.

GPU:

• No framebuffer.
• Uses a frame representation in the form of a 640x480x64 matrix, where each of the 64 bits indicates the intersection of a rectangle with a specific pixel, rect_left <= x < rect_right && rect_top <= y < rect_bottom for each rect for each pixel.
• Due to the properties of rectangles, the 640x480 matrix is represented as two arrays of 640 and 480 and is calculated during copying.
• During operation, the GPU obtains a 64-bit vector of rectangle collisions with the current pixel and passes the rectangle indices through a tree of multiplexers.
• The color is sent to the output based on the index from a mux tree.

Multiplexer tree diagram for 4 inputs:

Other:

• The main controller wakes up the CPU and resets the GPU.
• DMA Button controller copies the status of buttons to the data memory.
• DMA Rect copy preprocesses rectangle data and sends it to the GPU.
• Access to data memory is switched from the processor to the controllers near the vsync area.

Currently supported FPGA boards:

• Tang Nano 20K.
• Tang Primer 25K.

Although Tang Nano 9K has sufficient resources, for unknown reasons, I was unable to obtain a working version.

Board specific files are:

• src/brus16_top.sv (PLL)
• src/hdmi.sv
• src/bsram.sv (Data memory, BRAM instantination)
• src/prom.sv (Program memory, BRAM instantination)
• src/gpu/gpu_bram.sv (GPU internal memory, BRAM instantination)

If desired, the project can be adapted relatively quickly for another board.

system_clk clock frequency = 25.2 MHz.

If you are using Tang Nano 20K or Tang Primer 25K:

1. Generate program memory and data memory initialization files (game_code.mi, game_data.mi) from the game's binary file.

python tools/gen_fpga_firm.py game.bin game

2. Open the corresponding project (gowin/tn20k.gprj, gowin/tp25k.gprj).
3. Uncomment line 6 or 7 in the src/constants.svh file.
4. Generate prom (8192x16) for program memory and sdpb (8192x16) for data memory with default parameters, selecting game_code.mi for prom and game_data.mi for sdpb (choose board folder).
5. Run all and program your device.

Important project settings:

PMOD Joystick.

PMOD joystick: G11 PMOD group.

PMOD DVI: F5 PMOD group.

Simulation via Verilator.

Dependencies:

• C++ compiler
• verilator
• freeglut + freeglut-devel
• make

Uncomment SIM, DISABLE_CONTROLLERS and comment GOWIN, TP25K/TN20K.

Paste game data in data.txt and program.txt

Run:

verilator -f verilator_vga.f
make -j -C obj_dir -f Vbrus16_top.mk Vbrus16_top
./obj_dir/Vbrus16_top 

Dependencies:

• cocotb
• icarus verilog >= 13.0
• make

Run:

cd tests && make all