1.. SPDX-License-Identifier: GPL-2.0-only
2
3=============
4AD7380 driver
5=============
6
7ADC driver for Analog Devices Inc. AD7380 and similar devices. The module name
8is ``ad7380``.
9
10
11Supported devices
12=================
13
14The following chips are supported by this driver:
15
16* `AD7380 <https://www.analog.com/en/products/ad7380.html>`_
17* `AD7381 <https://www.analog.com/en/products/ad7381.html>`_
18* `AD7383 <https://www.analog.com/en/products/ad7383.html>`_
19* `AD7384 <https://www.analog.com/en/products/ad7384.html>`_
20* `AD7386 <https://www.analog.com/en/products/ad7386.html>`_
21* `AD7387 <https://www.analog.com/en/products/ad7387.html>`_
22* `AD7388 <https://www.analog.com/en/products/ad7388.html>`_
23* `AD7380-4 <https://www.analog.com/en/products/ad7380-4.html>`_
24* `AD7381-4 <https://www.analog.com/en/products/ad7381-4.html>`_
25* `AD7383-4 <https://www.analog.com/en/products/ad7383-4.html>`_
26* `AD7384-4 <https://www.analog.com/en/products/ad7384-4.html>`_
27* `AD7386-4 <https://www.analog.com/en/products/ad7386-4.html>`_
28* `AD7387-4 <https://www.analog.com/en/products/ad7387-4.html>`_
29* `AD7388-4 <https://www.analog.com/en/products/ad7388-4.html>`_
30
31
32Supported features
33==================
34
35SPI wiring modes
36----------------
37
38ad738x ADCs can output data on several SDO lines (1/2/4). The driver currently
39supports only 1 SDO line.
40
41Reference voltage
42-----------------
43
44ad7380-4
45~~~~~~~~
46
47ad7380-4 supports only an external reference voltage (2.5V to 3.3V). It must be
48declared in the device tree as ``refin-supply``.
49
50All other devices from ad738x family
51~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
52
53All other devices from ad738x support 2 possible reference voltage sources:
54
55- Internal reference (2.5V)
56- External reference (2.5V to 3.3V)
57
58The source is determined by the device tree. If ``refio-supply`` is present,
59then it is used as external reference, else the internal reference is used.
60
61Oversampling and resolution boost
62---------------------------------
63
64This family supports 2 types of oversampling: normal average and rolling
65average. Only normal average is supported by the driver, as rolling average can
66be achieved by processing a captured data buffer. The following ratios are
67available: 1 (oversampling disabled)/2/4/8/16/32.
68
69When the on-chip oversampling function is enabled the performance of the ADC can
70exceed the default resolution. To accommodate the performance boost achievable,
71it is possible to enable an additional two bits of resolution. Because the
72resolution boost feature can only be enabled when oversampling is enabled and
73oversampling is not as useful without the resolution boost, the driver
74automatically enables the resolution boost if and only if oversampling is
75enabled.
76
77Since the resolution boost feature causes 16-bit chips to now have 18-bit data
78which means the storagebits has to change from 16 to 32 bits, we use the new
79ext_scan_type feature to allow changing the scan_type at runtime. Unfortunately
80libiio does not support it. So when enabling or disabling oversampling, user
81must restart iiod using the following command:
82
83.. code-block:: bash
84
85	root:~# systemctl restart iiod
86
87Channel selection and sequencer (single-end chips only)
88-------------------------------------------------------
89
90Single-ended chips of this family (ad7386/7/8(-4)) have a 2:1 multiplexer in
91front of each ADC. They also include additional configuration registers that
92allow for either manual selection or automatic switching (sequencer mode), of
93the multiplexer inputs.
94
95From an IIO point of view, all inputs are exported, i.e ad7386/7/8
96export 4 channels and ad7386-4/7-4/8-4 export 8 channels.
97
98Inputs ``AinX0`` of multiplexers correspond to the first half of IIO channels (i.e
990-1 or 0-3) and inputs ``AinX1`` correspond to second half (i.e 2-3 or 4-7).
100Example for AD7386/7/8 (2 channels parts):
101
102.. code-block::
103
104	   IIO   | AD7386/7/8
105	         |         +----------------------------
106	         |         |     _____        ______
107	         |         |    |     |      |      |
108	voltage0 | AinA0 --|--->|     |      |      |
109	         |         |    | mux |----->| ADCA |---
110	voltage2 | AinA1 --|--->|     |      |      |
111	         |         |    |_____|      |_____ |
112	         |         |     _____        ______
113	         |         |    |     |      |      |
114	voltage1 | AinB0 --|--->|     |      |      |
115	         |         |    | mux |----->| ADCB |---
116	voltage3 | AinB1 --|--->|     |      |      |
117	         |         |    |_____|      |______|
118	         |         |
119	         |         +----------------------------
120
121
122When enabling sequencer mode, the effective sampling rate is divided by two.
123
124Unimplemented features
125----------------------
126
127- 2/4 SDO lines
128- Rolling average oversampling
129- Power down mode
130- CRC indication
131- Alert
132
133
134Device buffers
135==============
136
137This driver supports IIO triggered buffers.
138
139See :doc:`iio_devbuf` for more information.
140