@@ -191,3 +191,25 @@ Typical voltage channel attributes of a differential AD4000 series device:
+-------------------------------------------+------------------------------------------+
| ``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 the
+`AXI SPI Engine`_ to provide SPI offload support.
+
+.. _AXI SPI Engine: http://analogdevicesinc.github.io/hdl/projects/pulsar_adc/index.html
+
+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.
When SPI offloading is supported, the IIO device provides different sysfs interfaces to allow using the adjusting the sample rate. Document SPI offload support for AD4000 and similar devices. Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com> --- Documentation/iio/ad4000.rst | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+)