On Thu, 15 Aug 2024 12:11:57 +0000 Guillaume Stols <gstols@xxxxxxxxxxxx> wrote: > The Analog Devices Inc. AD7606 (and similar chips) are complex ADCs that > will benefit from a detailed driver documentation. > > This documents the current features supported by the driver. > > Signed-off-by: Guillaume Stols <gstols@xxxxxxxxxxxx> A few typos that I spotted, but other than that lgtm > --- > Documentation/iio/ad7606.rst | 142 +++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 142 insertions(+) > > diff --git a/Documentation/iio/ad7606.rst b/Documentation/iio/ad7606.rst > new file mode 100644 > index 000000000000..e9578399e80d > --- /dev/null > +++ b/Documentation/iio/ad7606.rst > @@ -0,0 +1,142 @@ > +.. SPDX-License-Identifier: GPL-2.0-only > + > +============= > +AD7606 driver > +============= > + > +ADC driver for Analog Devices Inc. AD7606 and similar devices. The module name > +is ``ad7606``. > + > +Supported devices > +================= > + > +The following chips are supported by this driver: > + > +* `AD7605 <https://www.analog.com/en/products/ad7605.html>`_ > +* `AD7606 <https://www.analog.com/en/products/ad7606.html>`_ > +* `AD7606B <https://www.analog.com/en/products/ad7606b.html>`_ > +* `AD7616 <https://www.analog.com/en/products/ad7616.html>`_ > + > +Supported features > +================== > + > +SPI wiring modes > +---------------- > + > +ad7606x ADCs can output data on several SDO lines (1/2/4/8). The driver > +currently supports only 1 SDO line. > + > +Parallel wiring mode > +-------------------- > + > +AD7606x ADC have also a parallel interface, with 16 lines (that can be reduced > +to 8 in byte mode). The parallel interface is selected by declaring the device > +as platform in the device tree (with no io-backends node defined, see below). > + > +IIO-backend mode > +---------------- > + > +This mode allows to reach the best sample rates, but it requires an external > +hardware (eg HDL or APU) to handle the low level communication. > +The backend mode is enabled when trough the definition of the "io-backends" through. Spell check in general as I'm bad at spotting these. > +property in the device tree. > +The reference configuration for the current implementation of IIO-backend mode > +is the HDL reference provided by ADI: > +https://wiki.analog.com/resources/eval/user-guides/ad7606x-fmc/hdl > +This implementation embeds an IIO-backend compatible IP (adi-axi-adc) and a PWM > +connected to the conversion trigger pin. > + > ++---+ +---------------------------- > +| | +-------+ |AD76xx > +| A | controls | | | > +| D |-------------->| PWM |-------------->| cnvst > +| 7 | | | | > +| 6 | +-------+ | > +| 0 | controls +-----------+------------ | > +| 6 |---------->| | |<--| frstdata > +| | | Backend | Backend |<--| busy > +| D | | Driver | | | > +| R | | | |-->| clk > +| I | requests |+---------+| DMA | | > +| V |----------->| Buffer ||<---- |<=>| DATA > +| E | |+---------+| | | > +| R | +-----------+-----------+ | > +| |-------------------------------------->| reset/configuration gpios > ++---+ +----------------------------- > + > + > +Software and hardware modes > +--------------------------- > + > +While all the AD7606 series parts can be configured using GPIOs, some of them > +can be configured using register. I'd add blank lines between paragraphs as makes it easier to read as text > +The chip that support software mode have more values avalaible for configuring available > +the device, as well as more settings, and allow to control the range and > +calibration per channel. > +The following settings are available per channel in software mode: > + - Scale > +Also, there is a broader choice of oversampling ratios in software mode. > + > +Conversion triggering > +--------------------- > + > +The conversion can be triggered by two distinct ways: > + > + - A GPIO is connected to the conversion trigger pin, and this GPIO is controlled > + by the driver directly. In this configuration, the driver set back the the driver sets back > + conversion trigger pin to high as soon as it has read all the conversions. > + > + - An external source is connected to the conversion trigger pin. In the > + current implementation, it must be a PWM. In this configuration, the driver > + does not control directly the conversion trigger pin. Instead, it can > + control the PWM's frequency. This trigger is enabled only for iio-backend. > + > +Reference voltage > +----------------- > + > +2 possible reference voltage sources are supported: > + > + - Internal reference (2.5V) > + - External reference (2.5V) > + > +The source is determined by the device tree. If ``refin-supply`` is present, > +then the external reference is used, else the internal reference is used. > + > +Oversampling > +------------ > + > +This family supports oversampling to improve SNR. > +In software mode, the following ratios are available: > +1 (oversampling disabled)/2/4/8/16/32/64/128/256. > + > +Unimplemented features > +---------------------- > + > +- 2/4/8 SDO lines > +- CRC indication > +- Calibration > + > +Device buffers > +============== > + > +IIO triggered buffer > +-------------------- > + > +This driver supports IIO triggered buffers, with a "built in" trigger, i.e the > +trigger is allocated and linked by the driver, and a new conversion is triggered > +as soon as the samples are transferred, and a timestamp channel is added to make > +up for the potential jitter induced by the delays in the interrupt handling. > + > +IIO backend buffer > +------------------ > + > +When IIO backend is used, the trigger is not needed, and the sample rate is > +considered as stable, hence there is no timestamp channel. The communication is > +delegated to an external logic, called a backend, and the backend's driver > +handles the buffer. When this mode is enabled, the driver cannot control the > +conversion pin, because the busy pin is bound to the backend. > + > + > + > + > + Drop this trailing whitespace. >
