我试图在它改变状态时使用它来读取 GPIO 值。
/sys/class/gpio/gpio499/value
我已经设置/sys/class/gpio/gpio499/edge
为两者
我正在尝试在一个单独的线程中使用poll命令监视值的变化。这是代码片段:
void PIN_gpio_poll(size_t gpio) //GPIO 499
{
char path[30];
char cValue;
int fd;
int ret_poll;
int ret_read;
struct pollfd pollfd;
int i;
pollfd.events = POLLPRI | POLLERR; /* look for GPIO status change. */
snprintf(path, 30, PHDRIVER_LINUX_CFG_DIR "/gpio%u/value", gpio);
fd = open(path, O_RDONLY);
if (fd == -1)
{
printf("Gpio_poll _ERROR\r\n");
}
pollfd.fd = fd;
ret_read = read(pollfd.fd, &cValue, 1); // Dummy Read to clear
while (1)
{
lseek(fd, 0, SEEK_SET);
ret_read = read(fd, &cValue, 1);
printf("Value=%c, RET READ=%d\n",cValue,ret_read);
// ret_poll = poll( &pollfd, 1, -1 );
ret_poll = poll( &pollfd, 1, 10000 ); //10sec timeout
printf("******REVENTS=%x\n",pollfd.revents);
if( ret_poll == -1 )
{
printf("Gpio_poll poll failed\r\n");
close(fd);
}else{
// if (pollfd.revents & POLLPRI )
{
lseek(fd, 0, SEEK_SET);
ret_read = read(pollfd.fd, &cValue, 1);
if(ret_read > 0)
{
printf("Cvalue = %c\n",cValue);
}
}
}
}
}
我面临的问题是,如果我将事件设置为POLLIN,则 poll 会立即返回。这是可以理解的,因为在值(0 或 1)GPIO中总是有要读取的数据。我提到 了https://www.kernel.org/doc/Documentation/gpio/sysfs.txt并将事件设置为 POLLPRI | 轮询。但在此方法中,轮询仅在超时后返回。当 GPIO 的值改变时它不会返回。有什么我在这里错过的诀窍吗?我也设置/sys/class/gpio/gpio499/edge
了上升,下降,但似乎没有任何效果。
编辑:这是输出grep -r . /sys/class/gpio/gpio499
/sys/class/gpio/gpio499/edge:both
/sys/class/gpio/gpio499/power/control:auto
/sys/class/gpio/gpio499/power/runtime_active_time:0
grep: /sys/class/gpio/gpio499/power/autosuspend_delay_ms: Input/output error
/sys/class/gpio/gpio499/power/runtime_status:unsupported
/sys/class/gpio/gpio499/power/runtime_suspended_time:0
/sys/class/gpio/gpio499/value:1
/sys/class/gpio/gpio499/active_low:0
/sys/class/gpio/gpio499/direction:in
注意:我想检测从 1 到 0 的值。