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tt_um_uacj — VGA Logo Bouncer

A Tiny Tapeout digital design that displays a 128×40 pixel bitmap logo bouncing around a 640×480 VGA screen, with real-time visual effects controlled via the input pins.

Overview

The design generates a standard VGA signal (640×480, 60 Hz) and animates a bitmap logo that bounces within the visible area, cycling through colors on each wall collision. Eight visual effects are individually controlled by the bits of ui_in.

Pinout

Inputs (`ui_in`)

Bit	Name	Description
0	`cfg_tile`	Tile mode: repeats the logo across the entire screen
1	`cfg_color`	Enables dynamic color palette
2	`cfg_invert`	Swaps foreground and background colors
3	`cfg_slow`	Halves the animation speed
4	`cfg_flip`	Flips the logo vertically
5	`cfg_checker`	Enables checkerboard background pattern
6	`cfg_scanline`	Simulates CRT scanlines
7	`cfg_glitch`	Enables the visual corruption (glitch) engine

Outputs (`uo_out`) — TinyVGA PMOD

Bits	Signal
`[7]`	HSYNC
`[6]`	B[0]
`[5]`	G[0]
`[4]`	R[0]
`[3]`	VSYNC
`[2]`	B[1]
`[1]`	G[1]
`[0]`	R[1]

Compatible with the standard Tiny Tapeout TinyVGA PMOD.

Bidirectionals (`uio_*`)

Not used. uio_out and uio_oe are held at 0.

Timing Parameters

Parameter	Value
Clock (`clk`)	25 MHz (40 ns period)
Reset	Active-low (`rst_n`)
Resolution	640 × 480 pixels
Refresh rate	~60 Hz
Logo size	128 × 40 pixels

Modules

`tt_um_uacj` (top)

Top-level module. Instantiates all submodules and implements:

Bounce logic: the logo starts at (200, 200) and travels diagonally. On each wall hit, the corresponding direction is reversed.
Collision flash: for 6 frames after a bounce, the logo is rendered in full white.
Speed divider (cfg_slow): when active, the logo advances one pixel every two frames.
Dynamic color: the color index increments on each bounce and is applied to the logo, background, and checkerboard pattern through the 8-color palette.

`hvsync_generator`

Generates horizontal and vertical sync signals according to the VGA standard:

Parameter	Value
H_DISPLAY	640
H_FRONT porch	16
H_SYNC	96
H_BACK porch	48
V_DISPLAY	480
V_BOTTOM border	10
V_SYNC	2
V_TOP border	33

Exposes hpos and vpos (10-bit each) and the display_on signal indicating when the beam is within the visible area.

`bitmap_rom`

A 640-byte read-only memory (40 rows × 16 bytes) storing the monochrome logo bitmap at 128×40 pixels (1 bpp).

Addressing: addr = y[5:0] * 16 + x[6:3]
Pixel extraction: pixel = mem[addr][x[2:0]]
Supports vertical flip via cfg_flip.

`palette`

An 8-entry LUT in 6-bit RRGGBB format (2 bits per channel):

Index	Color	Value
0	Cyan	`001011`
1	Pink	`110110`
2	Green	`101101`
3	Orange	`111000`
4	Purple	`110011`
5	Yellow	`011111`
6	Red	`110001`
7	White	`111111`

Instantiated three times: logo color, background color, and checkerboard color.

Glitch Engine

When cfg_glitch = 1, a visual corruption engine is activated based on an 8-bit LFSR (taps at positions 7, 5, 4, 3). The engine runs a 3-state FSM:

State	Description
0	Idle — waiting for a trigger
1	Active corruption (runs for `glitch_timer` frames)
2	Recovery (1-frame transition back to idle)

Effects applied during corruption:

Horizontal/vertical XOR scrambling: pixels are displaced using an LFSR-derived mask.
Horizontal tearing: selected rows are offset laterally by a pseudo-random amount.
Chromatic aberration: each RGB channel receives an independent XOR from the LFSR.
Channel swapping: R↔G and G↔B are permuted based on LFSR bits.
Inversion flash: at maximum intensity, colors are inverted on select frames.

The glitch engine also triggers automatically approximately every 150 frames while cfg_glitch = 1.

How to Use

Connect the TinyVGA PMOD to the uo_out pins.
Connect a VGA monitor to the PMOD.
Supply a 25 MHz clock on clk.
Assert rst_n = 0 briefly at startup, then release (rst_n = 1).
Control visual effects with the 8 bits of ui_in as described in the pinout table above.

Project Files

File	Description
`tt_um_uacj.v`	Top module: animation, effects, RGB output
`hvsync_generator.v`	VGA sync signal generator
`bitmap_rom.v`	Logo bitmap ROM (128×40, 1 bpp)
`palette.v`	8-color palette LUT
`config.json`	Tiny Tapeout build config (25 MHz clock)

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