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101 lines
2.4 KiB
101 lines
2.4 KiB
/** @file pulsate1.c
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@author M.P. Hayes
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@date 25 Sep 2013
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@brief Example of controlling pixel brightness with PWM.
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*/
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#include <stdlib.h>
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#include "system.h"
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#include "pacer.h"
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#include "led.h"
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#include "tinygl.h"
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/* This controls the range of luminance. A bigger number gives more
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dynamic range but requires a faster update rate. */
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#define LUMINANCE_STEPS 25
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/* This needs to be fast enough to prevent the eye noticing flicker.
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A lower value (say 5) is useful for flashing pixels. */
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#define PWM_RATE 40
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/* This is the rate (Hz) of luminance changes. */
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#define PULSATE_RATE 1
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#define UPDATE_RATE (LUMINANCE_STEPS * PWM_RATE)
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#define LOOP_RATE (TINYGL_WIDTH * UPDATE_RATE)
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/* Brightness = Luminance ** 2.5. */
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int main (void)
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{
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uint16_t pulsate_tick = 0;
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uint8_t pwm_tick = 0;
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uint8_t x;
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uint8_t y;
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uint8_t update_col = 0;
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uint8_t col;
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uint8_t luminance = 0;
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/* This controls the luminance levels. */
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const uint8_t levels[] = {4, 8, 16, 32, 64, 100, 64, 32, 16, 4};
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system_init ();
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tinygl_init (LOOP_RATE);
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led_init ();
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pacer_init (LOOP_RATE);
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while (1)
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{
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uint8_t state;
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/* Refresh display. */
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for (col = 0; col < TINYGL_WIDTH; col++)
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{
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pacer_wait ();
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tinygl_update ();
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if (update_col != col)
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continue;
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if (update_col == 0)
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update_col = TINYGL_WIDTH;
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update_col--;
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pulsate_tick++;
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if (pulsate_tick >= UPDATE_RATE / PULSATE_RATE)
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{
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pulsate_tick = 0;
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if (luminance == 0)
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luminance = ARRAY_SIZE (levels) - 1;
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else
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luminance--;
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}
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state = levels[luminance] > pwm_tick * 100 / LUMINANCE_STEPS;
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/* Pulse width modulate pixels to control luminance. */
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for (x = 0; x < TINYGL_WIDTH; x++)
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{
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for (y = 0; y < TINYGL_HEIGHT; y++)
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{
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tinygl_draw_point (tinygl_point (x, y), state);
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}
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}
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led_set (LED1, state);
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pwm_tick++;
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if (pwm_tick >= UPDATE_RATE / PWM_RATE)
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{
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pwm_tick = 0;
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}
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}
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}
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return 0;
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}
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