嵌入式系統 - gpio 相關

LED 燈號控制 (假定 LED 的 GPIO 為十進制的 34)

echo 34 > /sys/class/gpio/export            // 指定控制 gpio 34
echo out > /sys/class/gpio/gpio34/direction // 指定方向 (in, out)
echo 1 > /sys/class/gpio/gpio34/value   // 亮
echo 0 > /sys/class/gpio/gpio34/value   // 不亮

factory reset 按鍵 (假定 GPIO 為 9)

echo 9 > /sys/class/gpio/export     // 指定控制 gpio 9 (預設方向為 in，所以不用再指定方向)
cat /sys/class/gpio/gpio9/value     // 0: 未按壓, 1: 已按壓

列出所有 gpio 的內容

cat /sys/kernel/debug/gpio

使用 /dev/gpio 控制範例

static int doit = 0;
#define RALINK_GPIO_ENABLE_INTP         0x08
#define RALINK_GPIO_DISABLE_INTP        0x09
#define RALINK_GPIO_REG_IRQ             0x0A
typedef struct {
        unsigned int irq;               //request irq pin number
        pid_t pid;                      //process id to notify
} ralink_gpio_reg_info;
static void nvramIrqHandler(int signum)
{
        if (!doit && signum == SIGUSR2) {
            doit = 1;
            // todo ...
        }
}
int main(int argc, char **argv)
{
        int fd;
        ralink_gpio_reg_info info;

        signal(SIGUSR1, nvramIrqHandler);
        signal(SIGUSR2, nvramIrqHandler);

        fd = open("/dev/gpio", O_RDONLY);
        if (fd < 0) {
                perror("/dev/gpio");
                return -1;
        }

        //enable gpio interrupt
        if (ioctl(fd, RALINK_GPIO_ENABLE_INTP) < 0)
                goto ioctl_err;

        info.pid = getpid();
        info.irq = 18;

        //register gpio
        if (ioctl(fd, RALINK_GPIO_REG_IRQ, &info) < 0)
                goto ioctl_err;

        close(fd);

        while(1) {
                sleep(60);
        }
        return 0;

ioctl_err:
        perror("ioctl");
        close(fd);
        return -1;
}

FILE *fp;
if ((fptr = fopen("/proc/gpio","r"))) { // 0:not push, 1:push
    char buf[20];
    fgets(buf, sizeof(buf), fptr);
    sscanf(buf,"%d", &push_button);
    fclose(fptr);
}

使用 /dev/mem 控制範例

int _8a110_read_bt( void)
{
        int fd;
        void *smc_addr,*psmc_addr;
        u32 u32tmp;
        u8 u8tmp;

        if((fd = open("/dev/mem", O_RDWR | O_SYNC)) == -1)
                printf("open /dev/mem Error\n");

        psmc_addr = mmap(0, MAP_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED,\
                    fd,SMC_MAP_ADDRESS & ~MAP_MASK);

        if(psmc_addr == (void *) -1)
                printf("Memory mapped at address %p. Error\n", psmc_addr);

        smc_addr = psmc_addr + (SMC_MAP_ADDRESS & MAP_MASK);

        u32tmp = (*(volatile u32 *)(smc_addr));

        *(volatile u8 *)(smc_addr + GPIO_SW_ADDRESS) = 0x01; // set Multi PIN = GPIO
        write( fd, smc_addr + GPIO_SW_ADDRESS, 1);

        u8tmp = (*(volatile u8 *)(smc_addr + GPIO_SW_READ));

        if( munmap( psmc_addr, MAP_SIZE) == -1) {
                perror( " Error un-mmapping the file");
        }
        close(fd);

        if( u8tmp == 0x28) return 1;
        else return 0;

}

int _8a110_control_led(int hl)
{
        int fd;
        void *smc_addr,*psmc_addr;
        u32 u32tmp;

        if((fd = open("/dev/mem", O_RDWR | O_SYNC)) == -1)
                printf("open /dev/mem Error\n");

        psmc_addr = mmap(0, MAP_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED,\
                    fd,SMC_MAP_ADDRESS & ~MAP_MASK);

        if(psmc_addr == (void *) -1)
                printf("Memory mapped at address %p. Error\n", psmc_addr);

        smc_addr = psmc_addr + (SMC_MAP_ADDRESS & MAP_MASK);

        u32tmp = (*(volatile u32 *)(smc_addr));

        *(volatile u8 *)(smc_addr + PROGRAM_ADDRESS) = 0x01; // set Multi PIN = GPIO
        write( fd, smc_addr + PROGRAM_ADDRESS, 1);

        if (hl)
                *(volatile u8 *)(smc_addr + GPIO_LED_OFFSET) = 0x40; // LED OFF
        else
                *(volatile u8 *)(smc_addr + GPIO_LED_OFFSET) = 0x00; // LED ON
        write( fd, smc_addr + GPIO_LED_OFFSET, 1);

        if( munmap( psmc_addr, MAP_SIZE) == -1) {
                perror( " Error un-mmapping the file");
        }
        close(fd);

        return 0;
}