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A point of light oscillating in 2 perpendicular axes draws a pattern named "Lissajous Figure" (1857) or "Bowditch Curve" (1815). Patterns range from simple to complex depending on the frequency ratio and phase of the 2 axes. A 1:1 ratio with 0 phase difference draws a straight line at 45° angle. In this project the frequency ratio of the 2 axes slowly sweeps back and forth between 1:1 and 2:1. These patterns are easily generated with an oscilloscope and 2 sine wave oscillators. In the mid 1800's Joules Antoine Lissajous deflected a light beam with mirrors attached to tuning forks. He also created a SAND PENDULUM. This project displays Lissajous Figures on an 8x8 LED matrix (or 64 discrete LEDs for a larger device) and is driven by a PIC16F627 microcontroller.
PORTB pins of the mcu drive the 8 common anodes (X-axis). PORTA(Y-axis / LED cathodes) has a maximum of 7 pins configurable as outs. To obtain the necessary 8 outs, 2 pins PORTA <1:0> drive a decoder made with 3 nand gates(74HC00) which provides 3 outs from 2 pins of the mcu.
Pattern Table Read:
The "sine" motion of the pixel is obtained by reading a succession of 22 bytepatterns from a table in memory for the X-axis and the Y-axis respectively.
Link to HEX & ASM codes