1 .. SPDX-License-Identifier: GPL-2.0-only 2 3 ============= 4 AD7380 driver 5 ============= 6 7 ADC driver for Analog Devices Inc. AD7380 and similar devices. The module name 8 is ``ad7380``. 9 10 11 Supported devices 12 ================= 13 14 The 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 32 Supported features 33 ================== 34 35 SPI wiring modes 36 ---------------- 37 38 ad738x ADCs can output data on several SDO lines (1/2/4). The driver currently 39 supports only 1 SDO line. 40 41 Reference voltage 42 ----------------- 43 44 ad7380-4 45 ~~~~~~~~ 46 47 ad7380-4 supports only an external reference voltage (2.5V to 3.3V). It must be 48 declared in the device tree as ``refin-supply``. 49 50 All other devices from ad738x family 51 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 52 53 All 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 58 The source is determined by the device tree. If ``refio-supply`` is present, 59 then it is used as external reference, else the internal reference is used. 60 61 Oversampling and resolution boost 62 --------------------------------- 63 64 This family supports 2 types of oversampling: normal average and rolling 65 average. Only normal average is supported by the driver, as rolling average can 66 be achieved by processing a captured data buffer. The following ratios are 67 available: 1 (oversampling disabled)/2/4/8/16/32. 68 69 When the on-chip oversampling function is enabled the performance of the ADC can 70 exceed the default resolution. To accommodate the performance boost achievable, 71 it is possible to enable an additional two bits of resolution. Because the 72 resolution boost feature can only be enabled when oversampling is enabled and 73 oversampling is not as useful without the resolution boost, the driver 74 automatically enables the resolution boost if and only if oversampling is 75 enabled. 76 77 Since the resolution boost feature causes 16-bit chips to now have 18-bit data 78 which means the storagebits has to change from 16 to 32 bits, we use the new 79 ext_scan_type feature to allow changing the scan_type at runtime. Unfortunately 80 libiio does not support it. So when enabling or disabling oversampling, user 81 must restart iiod using the following command: 82 83 .. code-block:: bash 84 85 root:~# systemctl restart iiod 86 87 Channel selection and sequencer (single-end chips only) 88 ------------------------------------------------------- 89 90 Single-ended chips of this family (ad7386/7/8(-4)) have a 2:1 multiplexer in 91 front of each ADC. They also include additional configuration registers that 92 allow for either manual selection or automatic switching (sequencer mode), of 93 the multiplexer inputs. 94 95 From an IIO point of view, all inputs are exported, i.e ad7386/7/8 96 export 4 channels and ad7386-4/7-4/8-4 export 8 channels. 97 98 Inputs ``AinX0`` of multiplexers correspond to the first half of IIO channels (i.e 99 0-1 or 0-3) and inputs ``AinX1`` correspond to second half (i.e 2-3 or 4-7). 100 Example 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 | +---------------------------- 120 121 122 When enabling sequencer mode, the effective sampling rate is divided by two. 123 124 Unimplemented features 125 ---------------------- 126 127 - 2/4 SDO lines 128 - Rolling average oversampling 129 - Power down mode 130 - CRC indication 131 - Alert 132 133 134 Device buffers 135 ============== 136 137 This driver supports IIO triggered buffers. 138 139 See :doc:`iio_devbuf` for more information.
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