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Diffstat (limited to 'Documentation/iio/ad4000.rst')
| -rw-r--r-- | Documentation/iio/ad4000.rst | 91 |
1 files changed, 90 insertions, 1 deletions
diff --git a/Documentation/iio/ad4000.rst b/Documentation/iio/ad4000.rst index de8fd3ae6e62..c1d04d3436d2 100644 --- a/Documentation/iio/ad4000.rst +++ b/Documentation/iio/ad4000.rst @@ -4,7 +4,7 @@ AD4000 driver ============= -Device driver for Analog Devices Inc. AD4000 series of ADCs. +Device driver for Analog Devices Inc. AD4000 series of ADCs and similar devices. Supported devices ================= @@ -25,6 +25,21 @@ Supported devices * `AD4022 <https://www.analog.com/AD4022>`_ * `ADAQ4001 <https://www.analog.com/ADAQ4001>`_ * `ADAQ4003 <https://www.analog.com/ADAQ4003>`_ +* `AD7685 <https://www.analog.com/AD7685>`_ +* `AD7686 <https://www.analog.com/AD7686>`_ +* `AD7687 <https://www.analog.com/AD7687>`_ +* `AD7688 <https://www.analog.com/AD7688>`_ +* `AD7690 <https://www.analog.com/AD7690>`_ +* `AD7691 <https://www.analog.com/AD7691>`_ +* `AD7693 <https://www.analog.com/AD7693>`_ +* `AD7942 <https://www.analog.com/AD7942>`_ +* `AD7946 <https://www.analog.com/AD7946>`_ +* `AD7980 <https://www.analog.com/AD7980>`_ +* `AD7982 <https://www.analog.com/AD7982>`_ +* `AD7983 <https://www.analog.com/AD7983>`_ +* `AD7984 <https://www.analog.com/AD7984>`_ +* `AD7988-1 <https://www.analog.com/AD7988-1>`_ +* `AD7988-5 <https://www.analog.com/AD7988-5>`_ Wiring connections ------------------ @@ -129,3 +144,77 @@ Set ``adi,sdi-pin`` to ``"cs"`` to select this mode. ^ | | +--------------------| SCLK | +-------------+ + +IIO Device characteristics +========================== + +The AD4000 series driver supports differential and pseudo-differential ADCs. + +The span compression feature available in AD4000 series devices can be +enabled/disabled by changing the ``_scale_available`` attribute of the voltage +channel. Note that span compression configuration requires writing to AD4000 +configuration register, which is only possible when the ADC is wired in 3-wire +turbo mode, and the SPI controller is ``SPI_MOSI_IDLE_HIGH`` capable. If those +conditions are not met, no ``_scale_available`` attribute is provided. + +Besides that, differential and pseudo-differential voltage channels present +slightly different sysfs interfaces. + +Pseudo-differential ADCs +------------------------ + +Typical voltage channel attributes of a pseudo-differential AD4000 series device: + ++-------------------------------------------+------------------------------------------+ +| Voltage Channel Attributes | Description | ++===========================================+==========================================+ +| ``in_voltage0_raw`` | Raw ADC output code. | ++-------------------------------------------+------------------------------------------+ +| ``in_voltage0_offset`` | Offset to convert raw value to mV. | ++-------------------------------------------+------------------------------------------+ +| ``in_voltage0_scale`` | Scale factor to convert raw value to mV. | ++-------------------------------------------+------------------------------------------+ +| ``in_voltage0_scale_available`` | Toggles input span compression | ++-------------------------------------------+------------------------------------------+ + +Differential ADCs +----------------- + +Typical voltage channel attributes of a differential AD4000 series device: + ++-------------------------------------------+------------------------------------------+ +| Voltage Channel Attributes | Description | ++===========================================+==========================================+ +| ``in_voltage0-voltage1_raw`` | Raw ADC output code. | ++-------------------------------------------+------------------------------------------+ +| ``in_voltage0-voltage1_scale`` | Scale factor to convert raw value to mV. | ++-------------------------------------------+------------------------------------------+ +| ``in_voltage0-voltage1_scale_available`` | Toggles input span compression | ++-------------------------------------------+------------------------------------------+ + +SPI offload support +------------------- + +To be able to achieve the maximum sample rate, the driver can be used with SPI +offload engines such as the one usually present in `AXI SPI Engine`_, to provide +SPI offload support. + +.. _AXI SPI Engine: http://analogdevicesinc.github.io/hdl/projects/pulsar_adc/index.html + +To keep up with SPI offloading transfer speeds, the ADC must be connected either +in 3-wire turbo mode or in 3-wire without busy indicator mode and have SPI +controller CS line connected to the CNV pin. + +When set for SPI offload support, the IIO device will provide different +interfaces. + +* Either ``in_voltage0_sampling_frequency`` or + ``in_voltage0-voltage1_sampling_frequency`` file is provided to allow setting + the sample rate. +* IIO trigger device is not provided (no ``trigger`` directory). +* ``timestamp`` channel is not provided. + +Also, because the ADC output has a one sample latency (delay) when the device is +wired in "3-wire" mode and only one transfer per sample is done when using SPI +offloading, the first data sample in the buffer is not valid because it contains +the output of an earlier conversion result. |