Re: [PATCH v5 7/7] docs: iio: Add documentation for AD4000

Marcelo Schmitt
2024-06-28T14:38:39Z

On 06/26, David Lechner wrote:
> On 6/25/24 4:55 PM, Marcelo Schmitt wrote:
> > Document wiring configurations for the AD4000 series of ADCs.
> >
> > Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
> > ---
> > Documentation/iio/ad4000.rst | 131 +++++++++++++++++++++++++++++++++++
> > Documentation/iio/index.rst | 1 +
> > MAINTAINERS | 1 +
...
> > +Wiring connections
> > +------------------
> > +
> > +Devices of the AD4000 series can be connected to the SPI host controller in a
> > +few different modes.
> > +
> > +CS mode, 3-wire turbo mode
> > +^^^^^^^^^^^^^^^^^^^^^^^^^^
>
> The datasheet also has the same diagram in _Figure 55. CS Mode, 4-Wire Turbo Mode
> Connection Diagram_. So maybe we should call this "register support mode" or
> something like that instead of mentioning 3 or 4-wire?
>
Humm, ADAQ4003 datasheet has the same figure for CS Mode, 4-wire turbo mode
and CS mode, 4-wire with busy indicator although other datasheets have MOSI
to SDI in 4-wire turbo as you said. The register read/write functionality
sections say CNV must be brought low to access the configuration register.
I'll leave it as it is for now as I have not tested reg access with CNV high.
We can update this in the future if find out reg access to work in 4-wire mode.

> > +
> > +Datasheet "3-wire" mode is what most resembles standard SPI connection which,
> > +for these devices, comprises of connecting the controller CS line to device CNV
> > +pin and other SPI lines as usual. This configuration is (misleadingly) called
> > +"CS Mode, 3-Wire Turbo Mode" connection in datasheets.
> > +NOTE: The datasheet definition of 3-wire mode for the AD4000 series is NOT the
> > +same of standard spi-3wire mode.
> > +This is the only connection mode that allows configuration register access but
> > +it requires the SPI controller to support the ``SPI_MOSI_IDLE_HIGH`` feature.
> > +
> > +Omit the ``adi,sdi-pin`` property in device tree to select this mode.
> > +
> > +::
> > +
> > + +-------------+
> > + + ----------------------------------| SDO |
> > + | | |
> > + | +-------------------| CS |
> > + | v | |
> > + | +--------------------+ | HOST |
> > + | | CNV | | |
> > + +--->| SDI AD4000 SDO |-------->| SDI |
> > + | SCK | | |
> > + +--------------------+ | |
> > + ^ | |
> > + +--------------------| SCLK |
> > + +-------------+
> > +
>
> I think the rest of the explanations are good.
>