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* `ADAQ4370-4 <https://www.analog.com/en/products/adaq4370-4.html>`_ 31* `ADAQ4380-4 <https://www.analog.com/en/products/adaq4380-4.html>`_ 32 33 34Supported features 35================== 36 37SPI wiring modes 38---------------- 39 40ad738x ADCs can output data on several SDO lines (1/2/4). The driver currently 41supports only 1 SDO line. 42 43Reference voltage 44----------------- 45 46ad7380-4 47~~~~~~~~ 48 49ad7380-4 supports only an external reference voltage (2.5V to 3.3V). It must be 50declared in the device tree as ``refin-supply``. 51 52ADAQ devices 53~~~~~~~~~~~~ 54 55adaq4370-4 and adaq4380-4 don't have an external reference, but use a 3.3V 56internal reference derived from one of its supplies (``refin-supply``) 57 58All other devices from ad738x family 59~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 60 61All other devices from ad738x support 2 possible reference voltage sources: 62 63- Internal reference (2.5V) 64- External reference (2.5V to 3.3V) 65 66The source is determined by the device tree. If ``refio-supply`` is present, 67then it is used as external reference, else the internal reference is used. 68 69Oversampling and resolution boost 70--------------------------------- 71 72This family supports 2 types of oversampling: normal average and rolling 73average. Only normal average is supported by the driver, as rolling average can 74be achieved by processing a captured data buffer. The following ratios are 75available: 1 (oversampling disabled)/2/4/8/16/32. 76 77When the on-chip oversampling function is enabled the performance of the ADC can 78exceed the default resolution. To accommodate the performance boost achievable, 79it is possible to enable an additional two bits of resolution. Because the 80resolution boost feature can only be enabled when oversampling is enabled and 81oversampling is not as useful without the resolution boost, the driver 82automatically enables the resolution boost if and only if oversampling is 83enabled. 84 85Since the resolution boost feature causes 16-bit chips to now have 18-bit data 86which means the storagebits has to change from 16 to 32 bits, we use the new 87ext_scan_type feature to allow changing the scan_type at runtime. Unfortunately 88libiio does not support it. So when enabling or disabling oversampling, user 89must restart iiod using the following command: 90 91.. code-block:: bash 92 93 root:~# systemctl restart iiod 94 95Channel selection and sequencer (single-end chips only) 96------------------------------------------------------- 97 98Single-ended chips of this family (ad7386/7/8(-4)) have a 2:1 multiplexer in 99front of each ADC. They also include additional configuration registers that 100allow for either manual selection or automatic switching (sequencer mode), of 101the multiplexer inputs. 102 103From an IIO point of view, all inputs are exported, i.e ad7386/7/8 104export 4 channels and ad7386-4/7-4/8-4 export 8 channels. 105 106Inputs ``AinX0`` of multiplexers correspond to the first half of IIO channels (i.e 1070-1 or 0-3) and inputs ``AinX1`` correspond to second half (i.e 2-3 or 4-7). 108Example for AD7386/7/8 (2 channels parts): 109 110.. code-block:: 111 112 IIO | AD7386/7/8 113 | +---------------------------- 114 | | _____ ______ 115 | | | | | | 116 voltage0 | AinA0 --|--->| | | | 117 | | | mux |----->| ADCA |--- 118 voltage2 | AinA1 --|--->| | | | 119 | | |_____| |_____ | 120 | | _____ ______ 121 | | | | | | 122 voltage1 | AinB0 --|--->| | | | 123 | | | mux |----->| ADCB |--- 124 voltage3 | AinB1 --|--->| | | | 125 | | |_____| |______| 126 | | 127 | +---------------------------- 128 129 130When enabling sequencer mode, the effective sampling rate is divided by two. 131 132Gain (ADAQ devices only) 133~~~~~~~~~~~~~~~~~~~~~~~~ 134 135ADAQ devices have a pin selectable gain in front of each ADC. The appropriate 136gain is selectable from device tree using the ``adi,gain-milli`` property. 137Refer to the typical connection diagrams section of the datasheet for pin 138wiring. 139 140Unimplemented features 141---------------------- 142 143- 2/4 SDO lines 144- Rolling average oversampling 145- Power down mode 146- CRC indication 147- Alert 148 149 150Device buffers 151============== 152 153This driver supports IIO triggered buffers. 154 155See :doc:`iio_devbuf` for more information. 156