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| author | Martin Kelly <mkelly@xevo.com> | 2018-05-21 11:41:54 -0700 |
|---|---|---|
| committer | Jonathan Cameron <Jonathan.Cameron@huawei.com> | 2018-05-22 18:29:09 +0100 |
| commit | 96c92d42e9c93b2647d55b84ad883b11baa76307 (patch) | |
| tree | 75e467f4968fe110479a70d60266b8e296105218 /drivers/iio/imu | |
| parent | 9ff1d5009fc4b47ac0e6d7818dac0158e1804c3e (diff) | |
| download | linux-stable-96c92d42e9c93b2647d55b84ad883b11baa76307.tar.gz linux-stable-96c92d42e9c93b2647d55b84ad883b11baa76307.tar.bz2 linux-stable-96c92d42e9c93b2647d55b84ad883b11baa76307.zip | |
iio: imu: inv_mpu6050: add comment about frequencies
Although the driver allows frequencies between 4 and 1000 Hz, only the
frequencies advertised in the available frequencies file are backed
properly by a low-pass filter to prevent aliasing, so it's best to use
them. Since this is not obvious to the user, add a comment explaining
what's going on.
Signed-off-by: Martin Kelly <mkelly@xevo.com>
Acked-by: Jean-Baptiste Maneyrol <jmaneyrol@invensense.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Diffstat (limited to 'drivers/iio/imu')
| -rw-r--r-- | drivers/iio/imu/inv_mpu6050/inv_mpu_core.c | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c b/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c index 43fba5f7532b..f9c0624505a2 100644 --- a/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c +++ b/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c @@ -798,7 +798,14 @@ static const struct iio_chan_spec inv_mpu_channels[] = { INV_MPU6050_CHAN(IIO_ACCEL, IIO_MOD_Z, INV_MPU6050_SCAN_ACCL_Z), }; -/* constant IIO attribute */ +/* + * The user can choose any frequency between INV_MPU6050_MIN_FIFO_RATE and + * INV_MPU6050_MAX_FIFO_RATE, but only these frequencies are matched by the + * low-pass filter. Specifically, each of these sampling rates are about twice + * the bandwidth of a corresponding low-pass filter, which should eliminate + * aliasing following the Nyquist principle. By picking a frequency different + * from these, the user risks aliasing effects. + */ static IIO_CONST_ATTR_SAMP_FREQ_AVAIL("10 20 50 100 200 500"); static IIO_CONST_ATTR(in_anglvel_scale_available, "0.000133090 0.000266181 0.000532362 0.001064724"); |