Circlean/diode_controller/led.c

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C
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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <unistd.h>
/* GPIO registers address */
#define BCM2708_PERI_BASE 0x20000000
#define GPIO_BASE (BCM2708_PERI_BASE + 0x200000) /* GPIO controller */
#define BLOCK_SIZE (256)
/* GPIO setup macros. Always use GPIO_IN(x) before using GPIO_OUT(x) or GPIO_ALT(x,y) */
#define GPIO_IN(g) *(gpio+((g)/10)) &= ~(7<<(((g)%10)*3))
#define GPIO_OUT(g) *(gpio+((g)/10)) |= (1<<(((g)%10)*3))
#define GPIO_ALT(g,a) *(gpio+(((g)/10))) |= (((a)<=3?(a)+4:(a)==4?3:2)<<(((g)%10)*3))
#define GPIO_SET(g) *(gpio+7) = 1<<(g) /* sets bit which are 1, ignores bit which are 0 */
#define GPIO_CLR(g) *(gpio+10) = 1<<(g) /* clears bit which are 1, ignores bit which are 0 */
#define GPIO_LEV(g) (*(gpio+13) >> (g)) & 0x00000001
#define GPIO_4 4
int mem_fd;
void *gpio_map;
volatile uint32_t *gpio;
int main(int argc, char* argv[])
{
int ret;
int i;
/* open /dev/mem */
mem_fd = open("/dev/mem", O_RDWR|O_SYNC);
if (mem_fd == -1) {
perror("Cannot open /dev/mem");
exit(1);
}
/* mmap GPIO */
gpio_map = mmap(NULL, BLOCK_SIZE, PROT_READ|PROT_WRITE, MAP_SHARED, mem_fd, GPIO_BASE);
if (gpio_map == MAP_FAILED) {
perror("mmap() failed");
exit(1);
}
/* Always use volatile pointer! */
gpio = (volatile uint32_t *)gpio_map;
GPIO_IN(GPIO_4); /* must use GPIO_IN before we can use GPIO_OUT */
GPIO_OUT(GPIO_4);
//Turn on led
while (1) {
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//printf("Enable LED\n");
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GPIO_SET(GPIO_4);
usleep(1000000);
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//printf("Disable GPIO\n"); // Does not seem to work?
//GPIO_CLR(GPIO_4);
//usleep(1000000);
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}
/* Free up ressources */
/* munmap GPIO */
ret = munmap(gpio_map, BLOCK_SIZE);
if (ret == -1) {
perror("munmap() failed");
exit(1);
}
/* close /dev/mem */
ret = close(mem_fd);
if (ret == -1) {
perror("Cannot close /dev/mem");
exit(1);
}
return EXIT_SUCCESS;
}