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—resources:tools-software:linux-drivers:iio-adc:ad738x [17 Oct 2018 15:43] – created Stefan Popa
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 +====== AD738x IIO Dual Channel Serial ADC Linux Driver ======
  
 +===== Supported Devices =====
 +
 +  * [[adi>AD380]]
 +  * [[adi>AD381]]
 +  * [[adi>AD382]]
 +  * [[adi>AD383]]
 +  * [[adi>AD384]]
 +  * [[adi>AD385]]
 +  * [[adi>AD386]]
 +  * [[adi>AD387]]
 +  * [[adi>AD388]]
 +  * [[adi>AD380-4]]
 +  * [[adi>AD381-4]]
 +  * [[adi>AD382-4]]
 +  * [[adi>AD383-4]]
 +  * [[adi>AD384-4]]
 +  * [[adi>AD385-4]]
 +  * [[adi>AD386-4]]
 +  * [[adi>AD387-4]]
 +  * [[adi>AD388-4]]
 +===== Evaluation Boards =====
 +
 +  * [[adi>EVAL-AD738xFMCZ]]
 +
 +===== Description =====
 +
 +This is a Linux industrial I/O ([[software:linux:docs:iio:iio|IIO]]) subsystem driver, targeting dual or quad channel serial interface ADCs.
 +The industrial I/O subsystem provides a unified framework for drivers for many different types of converters and sensors using a number of different physical interfaces (i2c, spi, etc). 
 +See [[software:linux:docs:iio:iio|IIO]] for more information.
 +
 +====== Source Code ======
 +
 +===== Status =====
 +
 +^ Source ^ Mainlined? ^
 +| [[https://github.com/analogdevicesinc/linux/blob/master/drivers/iio/adc/ad738x.c|git]] | [No] |
 +
 +===== Files =====
 +
 +^ Function ^ File ^
 +| driver  | [[https://github.com/analogdevicesinc/linux/blob/master/drivers/iio/adc/ad738x.c]] |
 +
 +===== Devicetree =====
 +
 +Required devicetree properties:
 +  * compatible: Needs to be the name of the device. E.g. "ad7380"
 +  * reg: The chipselect number used for the device
 +  * spi-max-frequency: Maximum SPI clock frequency.
 +  * spi-cpol: Needs to be set for the correct SPI mode
 +  * vref-supply: Phandle to the fixed regulator
 +
 +<code>
 +        adc_vref: fixedregulator@0 {
 +         compatible = "regulator-fixed";
 + regulator-name = "fixed-supply";
 + regulator-min-microvolt = <2500000>;
 + regulator-max-microvolt = <2500000>;
 + regulator-boot-on;
 + };
 +
 + #address-cells = <1>;
 + #size-cells = <0>;
 + status = "okay";
 +
 + ad738x@0 {
 + compatible = "ad7380";
 + reg = <0>;
 + spi-max-frequency = <1000000>;
 + spi-cpol;
 + vref-supply = <&adc_vref>;
 + };
 +</code>
 +
 +====== Driver testing ======
 +
 +<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
 +<xterm>
 +root:/> **cd /sys/bus/iio/devices/**
 +root:/sys/bus/iio/devices> ls
 +iio:device0
 +
 +root:/sys/bus/iio/devices> **cd iio\:device0**
 +
 +root:/sys/bus/iio/devices/iio:device0> **ls -l**
 +drwxr-xr-x 2 root root    0 Sep 12 20:11 buffer
 +-r--r--r-- 1 root root 4096 Sep 12 20:11 dev
 +-rw-r--r-- 1 root root 4096 Sep 12 20:11 in_voltage0_raw
 +-rw-r--r-- 1 root root 4096 Sep 12 20:11 in_voltage1_raw
 +-rw-r--r-- 1 root root 4096 Sep 12 20:11 in_voltage_scale
 +-r--r--r-- 1 root root 4096 Sep 12 20:11 name
 +lrwxrwxrwx 1 root root    0 Sep 12 20:11 of_node -> ../../../../../../../../firmware/devicetree/base/soc/spi@7e204000/ad738x@0
 +drwxr-xr-x 2 root root    0 Sep 12 20:11 power
 +drwxr-xr-x 2 root root    0 Sep 12 20:11 scan_elements
 +lrwxrwxrwx 1 root root    0 Sep 12 20:11 subsystem -> ../../../../../../../../bus/iio
 +drwxr-xr-x 2 root root    0 Sep 12 20:11 trigger
 +-rw-r--r-- 1 root root 4096 Sep 12 20:11 uevent
 +</xterm></WRAP>
 +
 +=== Show device name ===
 +
 +<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
 +<xterm>
 +root:/sys/bus/iio/devices/iio:device0> **cat name**
 +ad7380
 +</xterm></WRAP>
 +
 +=== Show scale ===
 +
 +**Description:**\\
 +scale to be applied to in_voltage0_raw in order to obtain the measured voltage in millivolts.
 +
 +<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
 +<xterm>
 +root:/sys/bus/iio/devices/iio:device0> **cat in_voltage_scale**
 +0.076293945
 +</xterm></WRAP>
 +
 +=== Show channel 0 measurement ===
 +
 +**Description:**\\
 +Raw unscaled voltage measurement on channel 0
 +
 +<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
 +<xterm>
 +root:/sys/bus/iio/devices/iio:device0> **cat in_voltage0_raw**
 +28583
 +</xterm></WRAP>
 +
 +**U** = //in_voltage0_raw * in_voltage_scale// = 28583 * 0.076293945 = **2180.70 //mV//**
 +
 +===== Trigger management =====
 +
 +If deviceX supports triggered sampling, it’s a so called trigger consumer and there will be an additional folder /sys/bus/iio/device/iio:deviceX/trigger. In this folder there is a file called current_trigger, allowing controlling and viewing the current trigger source connected to deviceX. Available trigger sources can be identified by reading the name file /sys/bus/iio/devices/triggerY/name. The same trigger source can connect to multiple devices, so a single trigger may initialize data capture or reading from a number of sensors, converters, etc.
 +
 +This driver uses **high resolution timers** as interrupt source
 +
 +**Description:**\\
 +Hrtimer triggers creation and destruction
 +
 +Loading iio-trig-hrtimer module will register hrtimer trigger types allowing users to create hrtimer triggers:
 +
 +<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
 +<xterm>
 +root:/sys/kernel/config/iio/triggers/hrtimer/> **mkdir trigger0**
 +</xterm></WRAP>
 +
 +**Description:**\\
 +Read name of trigger0
 +
 +<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
 +<xterm>
 +root:/sys/bus/iio/devices/trigger0/> **cat name**
 +trigger0
 +</xterm></WRAP>
 +
 +**Description:**\\
 +Configure the sampling frequency of trigger0
 +
 +<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
 +<xterm>
 +root:/sys/bus/iio/devices/trigger0/> **echo 500 > sampling_frequency**
 +trigger0
 +</xterm></WRAP>
 +
 +**Description:**\\
 +Make trigger0 to current trigger of device0
 +
 +<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
 +<xterm>
 +root:/sys/bus/iio/devices/iio:device0/> **echo trigger0 > trigger/current_trigger **
 +</xterm></WRAP>
 +
 +**Description:**\\
 +Read current trigger source of device0
 +
 +<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
 +<xterm>
 +root:/sys/bus/iio/devices/iio:device0/trigger> **cat current_trigger**
 +trigger0 
 +</xterm></WRAP>
 +
 +===== Buffer management =====
 +
 +<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
 +<xterm>
 +root:/sys/bus/iio/devices/iio:device0/buffer> ls
 +**enable**          **length**                   **watermark**
 +root:/sys/bus/iio/devices/iio:device0/buffer>
 +</xterm></WRAP>
 +
 +Every buffer implementation features a set of files:
 +
 +**length**\\
 +Get/set the number of sample sets that may be held by the buffer.
 +
 +**enable**\\
 +Enables/disables the buffer. This file should be written last, after length and selection of scan elements
 +
 +**scan_elements**\\
 +The scan_elements directory contains interfaces for elements that will be captured for a single triggered sample set in the buffer.
 +
 +<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
 +<xterm>
 +root:/sys/bus/iio/devices/iio:device0/scan_elements> ls 
 +in_voltage0_en in_voltage0_index  in_voltage0_type  in_voltage1_en  in_voltage1_index in_voltage1_type
 +root:/sys/bus/iio/devices/iio:device0/scan_elements>
 +</xterm></WRAP>
 +
 +**in_voltageX_en / in_voltageX-voltageY_en / timestamp_en:**\\
 +Scan element control for triggered data capture. Writing 1 will enable the scan element, writing 0 will disable it
 +
 +**in_voltageX_type / in_voltageX-voltageY_type / timestamp_type:**\\
 +Description of the scan element data storage within the buffer and therefore in the form in which it is read from user-space. Form is [s|u]bits/storage-bits. s or u specifies if signed (2's complement) or unsigned. bits is the number of bits of data and storage-bits is the space (after padding) that it occupies in the buffer. Note that some devices will have additional information in the unused bits so to get a clean value, the bits value must be used to mask the buffer output value appropriately. The storage-bits value also specifies the data alignment. So u12/16 will be a unsigned 12 bit integer stored in a 16 bit location aligned to a 16 bit boundary. For other storage combinations this attribute will be extended appropriately.
 +
 +**in_voltageX_index / in_voltageX-voltageY_index / timestamp_index:**\\
 +A single positive integer specifying the position of this scan element in the buffer. Note these are not dependent on what is enabled and may not be contiguous. Thus for user-space to establish the full layout these must be used in conjunction with all _en attributes to establish which channels are present, and the relevant _type attributes to establish the data storage format.
 +
 +====== More Information ======
 +
 +{{page>software:linux:docs:iio:iio_snippets#iio pointers&noheader&firstseconly&noeditbtn}}
resources/tools-software/linux-drivers/iio-adc/ad738x.txt · Last modified: 29 Dec 2020 20:30 by Robin Getz

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