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====== AD7791 IIO Low Power Sigma-Delta ADC Linux Driver ======

===== Supported Devices =====

  * [[adi>AD7787]]
  * [[adi>AD7788]]
  * [[adi>AD7789]]
  * [[adi>AD7790]]
  * [[adi>AD7791]]

===== Reference Circuits =====

  * [[adi>CN0216]]
  * [[adi>CN0271]]

===== Evaluation Boards =====

  * [[adi>EVAL-AD7791EBZ]]

===== Description =====

This is a Linux industrial I/O ([[software:linux:docs:iio:iio|IIO]]) subsystem driver, targeting multi 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?  ^
| [[git.linux.org>drivers/iio/adc/ad7791.c|git]] |  [[git.linux.org>drivers/iio/adc/ad7791.c|Yes]]  |
===== Files =====

^ Function ^ File ^
| driver  | [[git.linux.org>>drivers/iio/adc/ad7791.c]] |
| include | [[git.linux.org>>include/linux/platform_data/ad7791.h]] |
====== Example platform device initialization ======

{{page>software/linux/docs/platform_and_bus_model#Platform Data&noheader&firstseconly&noeditbtn}}

<code c>
/**
 * struct ad7791_platform_data - AD7791 device platform data
 * @buffered: If set to true configure the device for buffered input mode.
 * @burnout_current: If set to true the 100mA burnout current is enabled.
 * @unipolar: If set to true sample in unipolar mode, if set to false sample in
 *      bipolar mode.
 */
struct ad7791_platform_data {
	bool buffered;
	bool burnout_current;
	bool unipolar;
};
</code>

<code c>
static struct ad7791_platform_data ad7791_pdata =  {
	.buffered = true,
	.burnout_current = false,
	.unipolar = false,
};
</code>

{{page>software/linux/docs/platform_and_bus_model#Declaring SPI slave devices&firstseconly&noeditbtn}}

Depending on the converter IC used, you may need to set the modalias accordingly, matching your part name.
It may also required to adjust max_speed_hz. Please consult the datasheet, for maximum spi clock supported by the device in question.

<code c>
static struct spi_board_info board_spi_board_info[] __initdata = {
	{
		.modalias = "ad7791",
		.max_speed_hz = 1000000,     /* max spi clock (SCK) speed in HZ */
		.bus_num = 0,
		.chip_select = 3, /* CS, change it for your board */
		.platform_data = &ad7791_pdata, /* No spi_driver specific config */
		.mode = SPI_MODE_3,
		.irq = IRQ_PF6,
	},
};
</code>

<code c>
static int __init board_init(void)
{
	[--snip--]

	spi_register_board_info(board_spi_board_info, ARRAY_SIZE(board_spi_board_info));

	[--snip--]

	return 0;
}
arch_initcall(board_init);
</code>

====== Adding Linux driver support ======

Configure kernel with "make menuconfig" (alternatively use "make xconfig" or
"make qconfig")

<WRAP round help>
The AD7791 Driver depends on **CONFIG_SPI**
</WRAP>

<code>
Linux Kernel Configuration
    Device Drivers  --->
        ...
        <*>     Industrial I/O support --->
            --- Industrial I/O support
            ...
            Analog to digital converters  ---> 
                ...
                <*>  Analog Devices AD7791 ADC driver
                ...
            ...
        ...
</code>
====== Hardware configuration ======

{{:resources:tools-software:linux-drivers:iio-adc:ad7791_eval_lr.jpg?600|}}
====== Driver testing ======

{{page>software:linux:docs:iio:iio_snippets#iio device files&noheader&firstseconly&noeditbtn}}

<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         trigger0

root:/sys/bus/iio/devices> **cd device0**

root:/sys/devices/platform/bfin-spi.0/spi0.3/iio:device0> **ls -l**
drwxr-xr-x    2 root     root             0 Jan  1 04:18 buffer
-r--r--r--    1 root     root          4096 Jan  1 04:18 dev
-rw-r--r--    1 root     root          4096 Jan  1 04:18 in_voltage-voltage_scale
-rw-r--r--    1 root     root          4096 Jan  1 04:18 in_voltage-voltage_shorted_scale
-rw-r--r--    1 root     root          4096 Jan  1 04:18 in_voltage0-voltage0_offset
-rw-r--r--    1 root     root          4096 Jan  1 04:18 in_voltage0-voltage0_raw
-rw-r--r--    1 root     root          4096 Jan  1 04:18 in_voltage0-voltage0_shorted_offset
-rw-r--r--    1 root     root          4096 Jan  1 04:18 in_voltage0-voltage0_shorted_raw
-rw-r--r--    1 root     root          4096 Jan  1 04:18 in_voltage1_supply_offset
-rw-r--r--    1 root     root          4096 Jan  1 04:18 in_voltage1_supply_raw
-rw-r--r--    1 root     root          4096 Jan  1 04:18 in_voltage_supply_scale
-r--r--r--    1 root     root          4096 Jan  1 04:18 name
drwxr-xr-x    2 root     root             0 Jan  1 04:18 power
-rw-r--r--    1 root     root          4096 Jan  1 04:18 sampling_frequency
-r--r--r--    1 root     root          4096 Jan  1 04:18 sampling_frequency_available
drwxr-xr-x    2 root     root             0 Jan  1 04:18 scan_elements
lrwxrwxrwx    1 root     root             0 Jan  1 04:18 subsystem -> ../../../../../../../bus/iio
drwxr-xr-x    2 root     root             0 Jan  1 04:18 trigger
-rw-r--r--    1 root     root          4096 Jan  1 04:18 uevent


root:/sys/devices/platform/bfin-spi.0/spi0.3/iio:device0>
</xterm></WRAP>

=== Show device name ===

<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
<xterm>
root:/sys/devices/platform/bfin-spi.0/spi0.3/iio:device0> **cat name**
ad7791
</xterm></WRAP>

=== Show available sampling frequencies / update rates ===

<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
<xterm>
root:/sys/devices/platform/bfin-spi.0/spi0.3/iio:device0> **cat sampling_frequency_available**
120 100 33.3 20 16.7 16.6 13.3 9.5
</xterm></WRAP>

=== Set sampling frequency / update rate ===

<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
<xterm>
root:/sys/devices/platform/bfin-spi.0/spi0.3/iio:device0> **cat sampling_frequency**
16.6
root:/sys/devices/platform/bfin-spi.0/spi0.3/iio:device0> **echo 100 > sampling_frequency**
root:/sys/devices/platform/bfin-spi.0/spi0.3/iio:device0> **cat sampling_frequency**
100
root:/sys/devices/platform/bfin-spi.0/spi0.3/iio:device0>
</xterm></WRAP>

=== Show supply voltage ===

**Description:**\\
Shows the AVDD supply voltage

<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
<xterm>
root:/sys/devices/platform/bfin-spi.0/spi0.3/iio:device0> **cat in_voltage1_supply_raw**
7817399
root:/sys/devices/platform/bfin-spi.0/spi0.3/iio:device0> **cat in_voltage_supply_scale**
0.000697374
</xterm></WRAP>

**U** = //(in_voltage1_supply_raw + in_voltage1_supply_offset) * in_voltage_supply_scale// = 7817399 * 0.000697374 = **3270.95608958 //mV//**

=== Show in_voltage0-voltage0_raw measurement ===

**Description:**\\
Raw unscaled voltage measurement on channel 0

^ ADC Input Pair ^ Channel name ^
| AIN(+) – AIN(–) | in_voltage0-voltage0_raw |
| AIN(-) - AIN(-) | in_voltage0-voltage0_shorted_raw |
| AVDD | in_voltage1_supply_raw |

<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
<xterm>
root:/sys/devices/platform/bfin-spi.0/spi0.3/iio:device0> **cat in_voltage0-voltage0_raw**
6710665
</xterm></WRAP>

**U** = //(in_voltage0-voltage0_raw + in_voltage0-voltage0_offset) * in_voltage-voltage_scale// = 6710665 * 0.000596046 = **999.95619165 //mV//**

===== Trigger management =====

<WRAP round help>
This driver only supports it's own default trigger source **ad7791-dev0**
</WRAP>

<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
<xterm>
root:/sys/devices/platform/bfin-spi.0/spi0.3/device0> **cat trigger/current_trigger** 
ad7791-dev0
</xterm></WRAP>

===== Buffer management =====

{{page>software:linux:docs:iio:iio_snippets#Buffer management&noheader&firstseconly&noeditbtn}}

<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
<xterm>
root:/sys/devices/platform/bfin-spi.0/spi0.3/iio:device0/scan_elements> **ls**
in_timestamp_en                     in_voltage0-voltage0_shorted_index
in_timestamp_index                  in_voltage0-voltage0_shorted_type
in_timestamp_type                   in_voltage0-voltage0_type
in_voltage0-voltage0_en             in_voltage1_supply_en
in_voltage0-voltage0_index          in_voltage1_supply_index
in_voltage0-voltage0_shorted_en     in_voltage1_supply_type

root:/sys/devices/platform/bfin-spi.0/spi0.3/iio:device0/scan_elements>
</xterm></WRAP>

{{page>software:linux:docs:iio:iio_snippets#Typical ADC scan elements&noheader&firstseconly&noeditbtn}}

====== More Information ======

{{page>software:linux:docs:iio:iio_snippets#iio pointers&noheader&firstseconly&noeditbtn}}
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