VHDL VGA Controller – Interactive Shapes

An FPGA project that implements a VGA controller capable of displaying 8 different shapes in 8 colors, with real-time movement and speed control using board buttons and switches.
Developed on a Digilent Nexys A7 FPGA.

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Features

• VGA output: 640×480 @ 60Hz (25 MHz pixel clock).
• 8 selectable shapes (via 3-bit switch).
• 8 selectable colors (via 3-bit RGB switches).
• Interactive movement: up, down, left, right, reset.
• Two movement speeds (selectable).
• Debounced button inputs for stable interaction.
• Fully modular VHDL design: reusable components.

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Project Structure

• main.vhd – Top-level entity (ties all modules together).
• SYNC.vhd – VGA timing generator (HSYNC, VSYNC, (x, y) counters).
• FREQ_DIV.vhd – Frequency divider (100 MHz → 25 MHz).
• Debouncer.vhd – Synchronizes button input with pixel clock.
• shape.vhd – Shape selector, color mux, drawing equations.
• SQUARE.vhd – Primitive example of a basic shape.

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User Controls

• Buttons:
  • UP / DOWN / LEFT / RIGHT – move shape.
  • RESET – reset position to screen center.
• Switches:
  • SW[2:0] – select shape (0–7).
  • SW[5:3] – select color (RGB palette).
  • SW[x] – speed selection (slow/fast).

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How Shapes Are Calculated

Shapes are rendered using equations on pixel coordinates (x, y) and shape center (cx, cy):

• Square/Rectangle: check pixel inside bounding box.
• Circle: (x - cx)² + (y - cy)² ≤ r².
• Triangle: edge functions (all signs equal).
• Other shapes: added by equations in shape.vhd.

Movement updates (cx, cy) registers per frame based on debounced button inputs and selected speed.