Question

以下shell命令切换Leopardboard gpio 31就好了：

echo 31 > /sys/class/gpio/export
echo out > /sys/class/gpio/gpio31/direction
echo 0 > /sys/class/gpio/gpio31/value
echo 1 > /sys/class/gpio/gpio31/value
echo 0 > /sys/class/gpio/gpio31/value

This用作以下代码的示例。知道为什么以下.vala代码不会切换gpio 31吗？

public void sync () {
    int fd = -1;
    fd = open("/sys/class/gpio/export", O_WRONLY);
    if (fd < 0) {
        GLib.stdout.printf("Error sync export\n");
        return;
    }
    write(fd, "31", 3);
    close(fd);
    fd = open("/sys/class/gpio/gpio31/direction", O_WRONLY);
    if (fd < 0) {
        GLib.stdout.printf("Error sync direction\n");
        return;
    }
    write(fd, "out", 4);
    close(fd);
    fd = open("/sys/class/gpio/gpio31/value", O_WRONLY);
    if (fd < 0) {
        GLib.stdout.printf("Error sync value\n");
        return;
    }
    write(fd, "0", 2);
    write(fd, "1", 2);
    Thread.usleep (1000); /* 1ms */
    write(fd, "0", 2);
    close(fd);
}

Answer 1

echo 31实际上会产生\ x33 \ x31 \ x0a，但您的write调用会写入\ x33 \ x31 \ x00。尝试这样的事情：

write(fd, "31\n", 3);

您还需要对write的其他来电进行类似的调整。

如何控制embedded-linux gpio？

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