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fade_leds.c
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fade_leds.c
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/*
* fade_leds.c
*
* Howdy Pierce, howdy@cardinalpeak.com
*
* Provide a pleasing fade-in / fade-out effect for a string of WS2812
* LEDs running on a Raspberry Pi. See the README for more
* information.
*
* This file requires the rpi_ws281x library, available at
* https://github.com/jgarff/rpi_ws281x
*/
#include <string.h>
#include <stdint.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include "ws2811.h"
#define TARGET_FREQ WS2811_TARGET_FREQ
#define GPIO_PIN 18
#define DMA 10
#define STRIP_TYPE WS2811_STRIP_GRB
#define LED_COUNT 5
#define STEPS 40
/* To prevent mulitple instances of fade_leds from stepping on each *
* other's DMA, fade_leds will wait until the following file is
* deleted until proceeding.
*/
#define SENTINEL_FILE "/tmp/fade_leds_sentinel"
ws2811_t ledstring =
{
.freq = TARGET_FREQ,
.dmanum = DMA,
.channel =
{
[0] =
{
.gpionum = GPIO_PIN,
.count = LED_COUNT,
.invert = 0,
.brightness = 255,
.strip_type = STRIP_TYPE,
},
[1] =
{
.gpionum = 0,
.count = 0,
.invert = 0,
.brightness = 0,
},
},
};
void set_color(unsigned int c)
{
ws2811_return_t ret;
int i;
for (i=0; i<LED_COUNT; i++) {
ledstring.channel[0].leds[i] = c;
}
if ((ret = ws2811_render(&ledstring)) != WS2811_SUCCESS) {
fprintf(stderr, "ws2811_render failed: %s\n", ws2811_get_return_t_str(ret));
return;
}
}
unsigned int newcolor(unsigned int old, unsigned int tgt, float step)
{
int r_old = (old & 0xFF0000) >> 16;
int g_old = (old & 0x00FF00) >> 8;
int b_old = (old & 0x0000FF);
int r_tgt = (tgt & 0xFF0000) >> 16;
int g_tgt = (tgt & 0x00FF00) >> 8;
int b_tgt = (tgt & 0x0000FF);
unsigned int r_new = r_old + (int)((r_tgt - r_old) * step);
unsigned int g_new = g_old + (int)((g_tgt - g_old) * step);
unsigned int b_new = b_old + (int)((b_tgt - b_old) * step);
return ((r_new << 16) | (g_new << 8) | b_new);
}
int test(unsigned int old, unsigned int tgt)
{
int i;
unsigned int res;
for (i=0; i<=10; i++) {
res = newcolor(old, tgt, i/10.0);
printf("0x%06x 0x%06x %0.3f 0x%06x\n", old, tgt, i/10.0, res);
}
}
void usage(char *bn)
{
fprintf(stderr, "Usage: %s color [color..]\n\n", bn);
fprintf(stderr, "Where each color is an RGB hex value of the form 0xFF1100\n");
fprintf(stderr, "The program will take one second to transition between each color pair\n");
exit(1);
}
int main(int argc, char *argv[])
{
ws2811_return_t ret;
unsigned int colors[20];
int num_colors = 0;
unsigned int c;
int i = 0;
int s;
int fd;
if (argc < 2)
usage(argv[0]);
for (i=1; i<argc; i++) {
if (sscanf(argv[i], "%x", &c) != 1) {
fprintf(stderr, "Could not resolve argument %s\n", argv[i]);
usage(argv[0]);
}
colors[i-1] = c;
}
num_colors = argc - 1;
/* atomically see if the test file exists */
while ((fd = open(SENTINEL_FILE, O_WRONLY | O_CREAT | O_EXCL, S_IRUSR)) < 0) {
if (errno != EEXIST) {
fprintf(stderr, "Error %d creating sentinel file %s: %s\n", errno,
SENTINEL_FILE, strerror(errno));
exit(1);
}
usleep(100000);
if (i++ > 300) {
fprintf(stderr, "Too long a wait for the sentinel file %s\n",
SENTINEL_FILE);
fprintf(stderr, "to disappear. If no other process is accessing the LEDs,\n");
fprintf(stderr, "try deleting this file by hand.\n");
exit(1);
}
}
close(fd);
if ((ret = ws2811_init(&ledstring)) != WS2811_SUCCESS) {
fprintf(stderr, "ws2811_init failed: %s\n", ws2811_get_return_t_str(ret));
return 1;
}
for (i=1; i<num_colors; i++) {
for (s=0; s<STEPS; s++) {
set_color(newcolor(colors[i-1], colors[i], (float)s/STEPS));
usleep(1000000 / STEPS);
}
set_color(colors[i]);
usleep(1000000 / STEPS);
}
ws2811_fini(&ledstring);
if (unlink(SENTINEL_FILE) < 0) {
fprintf(stderr, "Error %d removing sentinel file %s: %s\n", errno,
SENTINEL_FILE, strerror(errno));
exit(1);
}
exit(0);
}