Re: iio: imu new driver

[Lars-Peter Clausen <lars@metafoo.de>]

On 4/14/22 15:03, Jean-Baptiste Maneyrol wrote:
> Hello,
>
> accel and gyro are synchronized and are outputting data inside the same hardware FIFO, as inv_icm42600 is doing. The issue is that the sensors have different frequencies, using a header for signaling data availability, thus demultiplexing from userspace is not possible in a standard way.
>
> Solution found for inv_icm42600 was to use 2 devices with each one a buffer. FIFO is read, data demultiplexed, and sent in each device. Now that we can have 2 buffers for 1 device, is it simpler to use this solution rather than 2 devices?
>
> Thanks for your advice,
> JB

Hi,

So the data rates are synchronized, but different, i.e. integer ratios?

I think this might be a good use case to give the multi-buffer support a 
bit of real world testing.

- Lars


>
>
> From: Lars-Peter Clausen <lars@metafoo.de>
> Sent: Thursday, April 14, 2022 13:19
> To: Fawzi Khaber <Fawzi.Khaber@tdk.com>; jic23@kernel.org <jic23@kernel.org>
> Cc: Jean-Baptiste Maneyrol <Jean-Baptiste.Maneyrol@tdk.com>; linux-iio <linux-iio@vger.kernel.org>
> Subject: Re: iio: imu new driver
>   
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> ======================================================================
> On 4/14/22 12:35, Fawzi Khaber wrote:
>> Hello Jonathan,
>> We are currently implementing a new driver for an invensense chip similar to
>> iio/imu/inv_icm42600. The chip has 2 sensors a gyroscope and an
>> accelerometer, and we are wandering if it was better the have two
>> IIO devices, one for each sensor, or just one IIO device with two buffers.
> Are these two completely independent sensors that only sit in the same
> package or do they share a common clock and the data acquisition can be
> synchronized?
>
> If it is the latter the best might be to have a single device with a
> single buffer.
>
> Typical algorithms that process IMU data, like odometry, want to process
> the accelerator and gyroscope data jointly. If the data gets
> artificially separated into two buffers it first has to be re-aligned,
> which might be tricky to do.
>
> - Lars