1.. SPDX-License-Identifier: GPL-2.0-only 2 3============= 4AD4695 driver 5============= 6 7ADC driver for Analog Devices Inc. AD4695 and similar devices. The module name 8is ``ad4695``. 9 10 11Supported devices 12================= 13 14The following chips are supported by this driver: 15 16* `AD4695 <https://www.analog.com/AD4695>`_ 17* `AD4696 <https://www.analog.com/AD4696>`_ 18* `AD4697 <https://www.analog.com/AD4697>`_ 19* `AD4698 <https://www.analog.com/AD4698>`_ 20 21 22Supported features 23================== 24 25SPI wiring modes 26---------------- 27 28The driver currently supports the following SPI wiring configuration: 29 304-wire mode 31^^^^^^^^^^^ 32 33In this mode, CNV and CS are tied together and there is a single SDO line. 34 35.. code-block:: 36 37 +-------------+ +-------------+ 38 | CS |<-+------| CS | 39 | CNV |<-+ | | 40 | ADC | | HOST | 41 | | | | 42 | SDI |<--------| SDO | 43 | SDO |-------->| SDI | 44 | SCLK |<--------| SCLK | 45 +-------------+ +-------------+ 46 47To use this mode, in the device tree, omit the ``cnv-gpios`` and 48``spi-rx-bus-width`` properties. 49 50Channel configuration 51--------------------- 52 53Since the chip supports multiple ways to configure each channel, this must be 54described in the device tree based on what is actually wired up to the inputs. 55 56There are three typical configurations: 57 58An ``INx`` pin is used as the positive input with the ``REFGND``, ``COM`` or 59the next ``INx`` pin as the negative input. 60 61Pairing with REFGND 62^^^^^^^^^^^^^^^^^^^ 63 64Each ``INx`` pin can be used as a pseudo-differential input in conjunction with 65the ``REFGND`` pin. The device tree will look like this: 66 67.. code-block:: 68 69 channel@0 { 70 reg = <0>; /* IN0 */ 71 }; 72 73If no other channel properties are needed (e.g. ``adi,no-high-z``), the channel 74node can be omitted entirely. 75 76This will appear on the IIO bus as the ``voltage0`` channel. The processed value 77(*raw × scale*) will be the voltage present on the ``IN0`` pin relative to 78``REFGND``. (Offset is always 0 when pairing with ``REFGND``.) 79 80Pairing with COM 81^^^^^^^^^^^^^^^^ 82 83Each ``INx`` pin can be used as a pseudo-differential input in conjunction with 84the ``COM`` pin. The device tree will look like this: 85 86.. code-block:: 87 88 com-supply = <&vref_div_2>; 89 90 channel@1 { 91 reg = <1>; /* IN1 */ 92 common-mode-channel = <AD4695_COMMON_MODE_COM>; 93 bipolar; 94 }; 95 96This will appear on the IIO bus as the ``voltage1`` channel. The processed value 97(*(raw + offset) × scale*) will be the voltage measured on the ``IN1`` pin 98relative to ``REFGND``. (The offset is determined by the ``com-supply`` voltage.) 99 100The macro comes from: 101 102.. code-block:: 103 104 #include <dt-bindings/iio/adi,ad4695.h> 105 106Pairing two INx pins 107^^^^^^^^^^^^^^^^^^^^ 108 109An even-numbered ``INx`` pin and the following odd-numbered ``INx`` pin can be 110used as a pseudo-differential input. The device tree for using ``IN2`` as the 111positive input and ``IN3`` as the negative input will look like this: 112 113.. code-block:: 114 115 in3-supply = <&vref_div_2>; 116 117 channel@2 { 118 reg = <2>; /* IN2 */ 119 common-mode-channel = <3>; /* IN3 */ 120 bipolar; 121 }; 122 123This will appear on the IIO bus as the ``voltage2`` channel. The processed value 124(*(raw + offset) × scale*) will be the voltage measured on the ``IN1`` pin 125relative to ``REFGND``. (Offset is determined by the ``in3-supply`` voltage.) 126 127VCC supply 128---------- 129 130The chip supports being powered by an external LDO via the ``VCC`` input or an 131internal LDO via the ``LDO_IN`` input. The driver looks at the device tree to 132determine which is being used. If ``ldo-supply`` is present, then the internal 133LDO is used. If ``vcc-supply`` is present, then the external LDO is used and 134the internal LDO is disabled. 135 136Reference voltage 137----------------- 138 139The chip supports an external reference voltage via the ``REF`` input or an 140internal buffered reference voltage via the ``REFIN`` input. The driver looks 141at the device tree to determine which is being used. If ``ref-supply`` is 142present, then the external reference voltage is used and the internal buffer is 143disabled. If ``refin-supply`` is present, then the internal buffered reference 144voltage is used. 145 146Unimplemented features 147---------------------- 148 149- Additional wiring modes 150- Threshold events 151- Oversampling 152- Gain/offset calibration 153- GPIO support 154- CRC support 155 156Device buffers 157============== 158 159This driver supports hardware triggered buffers. This uses the "advanced 160sequencer" feature of the chip to trigger a burst of conversions. 161 162Also see :doc:`iio_devbuf` for more general information. 163