FPGA Mini-GPU with VGA Output

The Problem

Modern GPUs are incredibly powerful but also black boxes. As an ECE student, I wanted to understand graphics at the hardware level. Could I build a functional GPU from scratch using just an FPGA?

Constraints

Working with the Artix-7 FPGA meant dealing with:

Only 35K logic cells available
Limited to 225KB of Block RAM
Strict 60Hz timing requirements for VGA
No soft CPU - pure hardware implementation

Technical Approach

1. Display Controller

Implemented VGA timing generator with precise 25.175MHz pixel clock:

always @(posedge clk_25mhz) begin
    if (h_count < H_DISPLAY) 
        vga_active <= (v_count < V_DISPLAY);
    // Precise timing for 640x480@60Hz
end

2. Graphics Pipeline Architecture

Frame Buffer: Dual-port BRAM with double buffering to prevent tearing
Rasterizer: Hardware implementation of Bresenham line algorithm
Sprite Engine: DMA-style sprite blitting with transparency
Collision Detection: Parallel boundary checking in hardware

3. Host Communication

Python toolchain for development and debugging:

# Stream sprite data via UART
def upload_sprite(serial_port, sprite_data):
    header = struct.pack('>HH', width, height)
    serial_port.write(header + sprite_data)

Results & Performance

✅ 640×480 @ 60Hz stable VGA output
✅ 12-bit RGB color depth (4096 colors)
✅ 2 Games Running: Pong and Snake fully playable
✅ Less than 50% LUT Usage: Efficient resource utilization
✅ Zero frame drops with hardware double-buffering

Key Learnings

The biggest challenge was timing closure. The VGA specification requires exact timing - being off by even 0.1% causes display issues. I spent two weeks debugging why my display was shifted until I realized my pixel clock was 25.170MHz instead of 25.175MHz.

Another surprise was how much BRAM organization matters. Switching from a linear frame buffer to a tile-based approach improved fill rate by 3x.

What’s Next?

Currently implementing:

3D wireframe rendering
Texture mapping support
HDMI output upgrade
Custom GPU instruction set