Sensor utilities (sensor.h)

The following example demonstrates using elements from sensor.h to read the accelerometer sensor:

void sensor_read(void)
{
    const char* sensor_path = "/dev/sensor/accel";
    sensor_event_t se;
    int len = 0;

    // Check if this system contains the specified sensor.
    int rc = access(sensor_path, F_OK);
    if (-1 == rc) {
        fprintf(stderr, "error(%s) accessing path(%s)\n", strerror(errno),
           sensor_path);
        return;
    }

    // Open the sensor with read only access.
    // Leave the default for blocking read.
    int fd = open(sensor_path, O_RDONLY);
    if (-1 == fd) {
        fprintf(stderr, "error(%s) opening path(%s)\n", strerror(errno),
                sensor_path);
        return;
    }

    // Send the skip duplicate event device control.
    // The device must be moved for a new event to be sent.
    sensor_devctl_skipdupevent_u a_devctl;
    memset(&a_devctl, 0, sizeof(a_devctl));
    a_devctl.tx.enable = 1;
    rc = devctl(fd, DCMD_SENSOR_SKIPDUPEVENT, &a_devctl, sizeof(a_devctl),
                NULL);
    if (EOK != rc) {
        fprintf(stderr, "error(%s) attempting to skip duplicates\n",
                strerror(rc));
    }

    // Start an infinite loop.
    for (;;) {
        memset(&se, 0, sizeof(se));

        // Block waiting for new sensor data.
        len = read(fd, &se, sizeof(se));

        // Check for errors.
        if (-1 == len) {
            fprintf(stderr, "read error(%s)\n", strerror(errno));
            break;
        }
        if (len < sizeof(se)) {
            fprintf(stderr, "read size(%d) less then expected(%d)", len,
                    sizeof(se));
            continue;
        }
        if (SENSOR_TYPE_ACCELEROMETER != se.type) {
            fprintf(stderr, "received type(%d) different then expected(%d)",
                    se.type, SENSOR_TYPE_ACCELEROMETER);
            continue;
        }

        // Print out the payload by indexing into common structure.
        fprintf(stdout, "Acceleration->\tx:%+.2f\ty:%+.2f\tz:%+.2f\n",
                se.motion.dsp.x, se.motion.dsp.y, se.motion.dsp.z);
    }
}