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----------------- 43 442 possible reference voltage sources are supported: 45 46- Internal reference (2.5V) 47- External reference (2.5V to 3.3V) 48 49The source is determined by the device tree. If ``refio-supply`` is present, 50then the external reference is used, else the internal reference is used. 51 52Oversampling and resolution boost 53--------------------------------- 54 55This family supports 2 types of oversampling: normal average and rolling 56average. Only normal average is supported by the driver, as rolling average can 57be achieved by processing a captured data buffer. The following ratios are 58available: 1 (oversampling disabled)/2/4/8/16/32. 59 60When the on-chip oversampling function is enabled the performance of the ADC can 61exceed the default resolution. To accommodate the performance boost achievable, 62it is possible to enable an additional two bits of resolution. Because the 63resolution boost feature can only be enabled when oversampling is enabled and 64oversampling is not as useful without the resolution boost, the driver 65automatically enables the resolution boost if and only if oversampling is 66enabled. 67 68Since the resolution boost feature causes 16-bit chips to now have 18-bit data 69which means the storagebits has to change from 16 to 32 bits, we use the new 70ext_scan_type feature to allow changing the scan_type at runtime. Unfortunately 71libiio does not support it. So when enabling or disabling oversampling, user 72must restart iiod using the following command: 73 74.. code-block:: bash 75 76 root:~# systemctl restart iiod 77 78Channel selection and sequencer (single-end chips only) 79------------------------------------------------------- 80 81Single-ended chips of this family (ad7386/7/8(-4)) have a 2:1 multiplexer in 82front of each ADC. They also include additional configuration registers that 83allow for either manual selection or automatic switching (sequencer mode), of 84the multiplexer inputs. 85 86From an IIO point of view, all inputs are exported, i.e ad7386/7/8 87export 4 channels and ad7386-4/7-4/8-4 export 8 channels. 88 89Inputs ``AinX0`` of multiplexers correspond to the first half of IIO channels (i.e 900-1 or 0-3) and inputs ``AinX1`` correspond to second half (i.e 2-3 or 4-7). 91Example for AD7386/7/8 (2 channels parts): 92 93.. code-block:: 94 95 IIO | AD7386/7/8 96 | +---------------------------- 97 | | _____ ______ 98 | | | | | | 99 voltage0 | AinA0 --|--->| | | | 100 | | | mux |----->| ADCA |--- 101 voltage2 | AinA1 --|--->| | | | 102 | | |_____| |_____ | 103 | | _____ ______ 104 | | | | | | 105 voltage1 | AinB0 --|--->| | | | 106 | | | mux |----->| ADCB |--- 107 voltage3 | AinB1 --|--->| | | | 108 | | |_____| |______| 109 | | 110 | +---------------------------- 111 112 113When enabling sequencer mode, the effective sampling rate is divided by two. 114 115Unimplemented features 116---------------------- 117 118- 2/4 SDO lines 119- Rolling average oversampling 120- Power down mode 121- CRC indication 122- Alert 123 124 125Device buffers 126============== 127 128This driver supports IIO triggered buffers. 129 130See :doc:`iio_devbuf` for more information. 131