716 Katomata - 1D Cellular Automata :: Quicker, easier and cheaper to make your own chip!

How it works

Katomata is a Tiny Tapeout demoscene entry: a 1D elementary cellular automata visualizer for VGA. It implements Stephen Wolfram's classification of Elementary Cellular Automata and continuously cycles through all 256 rules (rule 0 through rule 255), drawing the time evolution of each rule directly on a 640x480 @ 60 Hz VGA frame.

Cellular automata, briefly

A 1D elementary cellular automaton is a row of binary cells that evolves in discrete steps. The next state of each cell is decided by its own state and that of its two immediate neighbours - three bits in, one bit out, so 2^3 = 8 input patterns and one output bit per pattern. Packing those 8 output bits into a byte gives 2^8 = 256 possible "rules", numbered 0-255. Rule 30 (the default starting rule here) is famously chaotic; rule 90 produces a Sierpinski triangle; rule 110 is Turing complete.

What you see on screen

A row of 32 cells spans the visible width of the frame (each cell is 20x20 pixels).
Each successive row of the screen is the next generation of the automaton, computed combinationally from the row above by the automata_engine module using the current rule byte.
The active rule is held for 100 frames (~1.67 s), then advances by one. After rule 255 it wraps back to rule 0.
Halfway through each rule's display the seed pattern is inverted, so every rule is shown both starting from a single black cell on white and a single white cell on black.
Foreground/background colors are derived from the current rule byte, so each of the 256 rules has a distinct look.
The bottom 20-pixel strip is a rule indicator: it shows the current rule number in binary as 8 large cells, MSB on the left.

Modules

tt_um_katomata (top): VGA pipeline, framing logic, rule sequencer, color mapping.
hvsync_generator: standard 640x480 @ 60 Hz horizontal/vertical sync generator (with an added vmaxxed end-of-frame strobe).
automata_engine: pure-combinational 1->1 row update for the selected rule byte.
counter_gen, pos_edge_detect, neg_edge_detect: small reusable helpers.

How to test

Plug a TinyVGA Pmod into the output Pmod connector of the Tiny Tapeout demo board.
Drive clk with a 25.175 MHz pixel clock.
Hold rst_n low briefly to reset, then release.
Connect a VGA monitor. You should see the cellular automata rules scrolling top-to-bottom, with the rule indicator strip across the bottom of the screen advancing roughly every 1.67 seconds.

There are no input pins to drive - all 8 ui_in and 8 uio_in bits are unused.

External hardware

TinyVGA Pmod on the output Pmod connector.
A VGA monitor.

#	Input	Output	Bidirectional
0		R1
1		G1
2		B1
3		VSync
4		R0
5		G0
6		B0
7		HSync

716 Katomata - 1D Cellular Automata