android - 如何从/dev/iio中的LSM330读取数据:deviceX?

我正在尝试在i.MX6板上连接LSM330加速度计/陀螺仪模块。该模块连接到I2C总线，设备树文件的相关部分如下:

&i2c1 {
    clock-frequency = <100000>;
    pinctrl-names = "default";
    pinctrl-0 = <&pinctrl_i2c1_2>;
    status = "okay";

    /* LSM330 motion detector (accelerometer) */
    lsm330_accel: lsm330_accel@0x1e {
        compatible = "st,lsm330-accel";
        st,drdy-int-pin = <1>;
        reg = <0x1e>;
    };

    /* LSM330 motion detector (gyroscope) */
    lsm330_gyro: lsm330_gyro@0x6a {
        compatible = "st,lsm330-gyro";
        st,drdy-int-pin = <2>;
        reg = <0x6a>;
    };
};

该模块显示为加速度计的/dev/iio:device0和陀螺仪的/dev/iio:device1。它们还显示为/sys/bus/iio/devices/iio:device0和/sys/bus/iio/devices/iio:device1。我可以通过cat in_accel_x_raw等获取传感器读数。但是，运行cat /dev/iio:device0会立即返回并且不产生任何输出。

在Internet上搜索之后，我还尝试了以下命令:

cd /sys/bus/iio/devices/iio_sysfs_trigger
echo 0 > add_trigger
cd /sys/bus/iio/devices/iio:device0
echo 1 > scan_elements/in_accel_x_en
echo 1 > scan_elements/in_accel_y_en
echo 1 > scan_elements/in_accel_z_en
echo 1 > scan_elements/in_timestamp_en
echo sysfstrig0 > trigger/current_trigger
echo 100 > buffer/length
echo 1 > buffer/enable
echo 1 > /sys/bus/iio/devices/trigger0/trigger_now

这应该设置通道，启用缓冲区并向缓冲区中获取一些读数。据我所知，cat /dev/iio:device0应该显示缓冲区，但是它给了我Device or resource busy。使用cat /sys/bus/iio/devices/iio:device0/in_accel_x_raw从内核进行的进一步读取不再起作用，并给出相同的错误消息。

我是Linux内核的新手，我的目标是将传感器数据公开给Android系统，以便用户可以旋转屏幕等。如何获得Android以从模块中获取传感器读数？

最佳答案

查看android logcat之后，事实证明Android HAL没有读取或写入sysfs中目录的权限。我最终将一堆chmod命令放入init.rc文件中，以便Android可以访问传感器数据。

# Change permissions for the LSM330 sysfs entries (accelerometer)
chmod 0666 /sys/bus/iio/devices/iio\:device0/sampling_frequency
chmod 0666 /sys/bus/iio/devices/iio\:device0/buffer/enable
chmod 0666 /sys/bus/iio/devices/iio\:device0/buffer/length
chmod 0666 /sys/bus/iio/devices/iio\:device0/trigger/current_trigger
chmod 0666 /sys/bus/iio/devices/iio\:device0/scan_elements/in_accel_x_en
chmod 0666 /sys/bus/iio/devices/iio\:device0/scan_elements/in_accel_y_en
chmod 0666 /sys/bus/iio/devices/iio\:device0/scan_elements/in_accel_z_en
chmod 0666 /sys/bus/iio/devices/iio\:device0/scan_elements/in_timestamp_en
chmod 0666 /dev/iio\:device0

希望这对某人有帮助。

IIO

android - 如何从/dev/iio中的LSM330读取数据:deviceX?