On Wed, 16 May 2018 09:07:53 -0700
Martin Kelly <mkelly@xxxxxxxx> wrote:
> On 05/16/2018 12:51 AM, Jean-Baptiste Maneyrol wrote:
> >
> >
> > On 15/05/2018 23:53, Martin Kelly wrote:
> >> CAUTION: This email originated from outside of the organization.
> >> Please make sure the sender is who they say they are and do not click
> >> links or open attachments unless you recognize the sender and know the
> >> content is safe.
> >>
> >>
> >> Currently, we allow a minimum FIFO rate of 4 and a max of 1000, but we
> >> advertise down to only 10 and up to 1000. Expand the advertised range to
> >> reflect the full available range.
> >>
> >> Signed-off-by: Martin Kelly <mkelly@xxxxxxxx>
> >> ---
> >> drivers/iio/imu/inv_mpu6050/inv_mpu_core.c | 2 +-
> >> 1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c
> >> b/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c
> >> index 43fba5f7532b..3f4862f09db3 100644
> >> --- a/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c
> >> +++ b/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c
> >> @@ -799,7 +799,7 @@ static const struct iio_chan_spec
> >> inv_mpu_channels[] = {
> >> };
> >>
> >> /* constant IIO attribute */
> >> -static IIO_CONST_ATTR_SAMP_FREQ_AVAIL("10 20 50 100 200 500");
> >> +static IIO_CONST_ATTR_SAMP_FREQ_AVAIL("4 10 20 50 100 200 500 1000");
> >> static IIO_CONST_ATTR(in_anglvel_scale_available,
> >> "0.000133090 0.000266181
> >> 0.000532362 0.001064724");
> >> static IIO_CONST_ATTR(in_accel_scale_available,
> >> --
> >> 2.11.0
> >>
> >
> > Hello,
> >
> > in fact we advertise only frequencies that are supported by the low-pass
> > filter. Filter bandwidths are: 5Hz, 10Hz, 20Hz, 42Hz (~50), 98Hz (~100),
> > 188Hz (~200), which are corresponding to a sampling rate of (x2): 10Hz,
> > 20Hz, ~50Hz, ~200Hz, ~400Hz. Only 500Hz is a little out of specs, since
> > 400Hz is not a possible frequency.
> >
> > You can always set the frequency to any supported values, but you can
> > suffer from aliasing.
> >
> > I strongly suggest we just keep it like it is today. Better not
> > advertise frequencies that are not correctly filtered.
> >
> > JB
>
> OK, that makes sense and is fine with me. Perhaps I should instead just
> add a comment explaining the situation, since I couldn't tell from the
> code itself.
Hmm. If this wasn't already the case I would advocate never allowing the
user to pick frequencies where the device effectively won't work properly.
Ah well, too late now as they are in the ABI. Agreed a comment would
avoid anyone trying to figure this out in future.
Jonathan
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