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====== AD7476A IIO Single Channel Serial ADC Linux Driver ======

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


  * [[adi>AD7091R]]
  * [[adi>AD7273]]
  * [[adi>AD7274]]
  * [[adi>AD7276]]
  * [[adi>AD7277]]
  * [[adi>AD7278]]
  * [[adi>AD7466]]
  * [[adi>AD7467]]
  * [[adi>AD7468]]
  * [[adi>AD7475]]
  * [[adi>AD7476]]
  * [[adi>AD7476A]]
  * [[adi>AD7477]]
  * [[adi>AD7477A]]
  * [[adi>AD7478]]
  * [[adi>AD7478A]]
  * [[adi>AD7495]]
  * [[adi>AD7680]]
  * [[adi>AD7683]]
  * [[adi>AD7684]]
  * [[adi>AD7685]]
  * [[adi>AD7686]]
  * [[adi>AD7687]]
  * [[adi>AD7688]]
  * [[adi>AD7690]]
  * [[adi>AD7691]]
  * [[adi>AD7693]]
  * [[adi>AD7694]]
  * [[adi>AD7910]]
  * [[adi>AD7920]]
  * [[adi>AD7940]]
  * [[adi>AD7942]]
  * [[adi>AD7946]]
  * [[adi>AD7980]]
  * [[adi>AD7982]]
  * [[adi>AD7984]]
  * [[adi>AD7985]]
  * [[adi>AD7988-1]]
  * [[adi>AD7988-5]]
  * [[adi>LTC2314-14]]

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

  * [[adi>CN0104]]
  * [[adi>CN0130]]
  * [[adi>CN0178]]
  * [[adi>CN0180]]
  * [[adi>CN0194]]
  * [[adi>CN0213]]
  * [[adi>CN0225]]
  * [[adi>CN0237]]
  * [[adi>CN0241]]
  * [[adi>CN0247]]
  * [[adi>CN0255]]
  * [[adi>CN0260]]
  * [[adi>CN0261]]
  * [[adi>CN0269]]
  * [[adi>CN0305]]
  * [[adi>CN0306]]
  * [[adi>CN0335]]
  * [[adi>CN0336]]
  * [[adi>CN0337]]
  * [[adi>CN0350]]
  * [[adi>CN0366]]
===== Evaluation Boards =====

  * [[adi>EVAL-AD7091RSDZ]]
  * [[adi>EVAL-AD7276SDZ]]
  * [[adi>EVAL-AD7466]]
  * [[adi>EVAL-AD7476A]]
  * [[adi>EVAL-AD7477]]
  * [[adi>EVAL-AD7910]]
  * [[adi>EVAL-AD7920]]
  * [[adi>EVAL-AD7942]]
  * [[adi>EVAL-AD7683SDZ]]
  * [[adi>EVAL-AD7684SDZ]]
  * [[adi>EVAL-AD7685SDZ]]
  * [[adi>EVAL-AD7686SDZ]]
  * [[adi>EVAL-AD7687SDZ]]
  * [[adi>EVAL-AD7688SDZ]]
  * [[adi>EVAL-AD7690SDZ]]
  * [[adi>EVAL-AD7691SDZ]]
  * [[adi>EVAL-AD7693SDZ]]
  * [[adi>EVAL-AD7694SDZ]]
  * [[adi>EVAL-AD7942SDZ]]
  * [[adi>EVAL-AD7946SDZ]]
  * [[adi>EVAL-AD7980SDZ]]
  * [[adi>EVAL-AD7982SDZ]]
  * [[adi>EVAL-AD7984SDZ]]
  * [[adi>EVAL-AD7985EBZ]]
  * [[adi>EVAL-AD7988-5SDZ]]
===== Description =====

This is a Linux industrial I/O ([[software:linux:docs:iio:iio|IIO]]) subsystem driver, targeting single 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/ad7476.c|git]] | [[git.linux.org>drivers/iio/adc/ad7476.c|Yes]] |

===== Files =====

^ Function ^ File ^
| driver  | [[git.linux.org>drivers/iio/adc/ad7476.c]] |

====== Example platform device initialization ======

===== Specifying reference voltage via the regulator framework =====

Below example specifies a 3.3 Volt reference for the SPI device 3 on SPI-Bus 0. (**spi0.3**)

<code c>
#if defined(CONFIG_REGULATOR_FIXED_VOLTAGE) || defined(CONFIG_REGULATOR_FIXED_VOLTAGE_MODULE)
static struct regulator_consumer_supply ad7476_consumer_supplies[] = {
	REGULATOR_SUPPLY("vcc", "spi0.3"),
};

static struct regulator_init_data stamp_avdd_reg_init_data = {
	.constraints	= {
		.name	= "3V3",
		.valid_ops_mask = REGULATOR_CHANGE_STATUS,
	},
	.consumer_supplies = ad7476_consumer_supplies,
	.num_consumer_supplies = ARRAY_SIZE(ad7476_consumer_supplies),
};

static struct fixed_voltage_config stamp_vdd_pdata = {
	.supply_name	= "board-3V3",
	.microvolts	= 3300000,
	.gpio		= -EINVAL,
	.enabled_at_boot = 0,
	.init_data	= &stamp_avdd_reg_init_data,
};
static struct platform_device brd_voltage_regulator = {
	.name		= "reg-fixed-voltage",
	.id		= -1,
	.num_resources	= 0,
	.dev		= {
		.platform_data	= &stamp_vdd_pdata,
	},
};
#endif
</code>

<code c>
static struct platform_device *board_devices[] __initdata = {
#if defined(CONFIG_REGULATOR_FIXED_VOLTAGE) || defined(CONFIG_REGULATOR_FIXED_VOLTAGE_MODULE)
	&brd_voltage_regulator
#endif
};
</code>


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

	platform_add_devices(board_devices, ARRAY_SIZE(board_devices));

	[--snip--]

	return 0;
}
arch_initcall(board_init);
</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 = {
#if defined(CONFIG_AD7476) || \
 	defined(CONFIG_AD7476_MODULE)
	{
		/* the modalias must be the same as spi device driver name */
		.modalias = "ad7476", /* Name of spi_driver for this device */
		.max_speed_hz = 1000000,     /* max spi clock (SCK) speed in HZ */
		.bus_num = 0, /* Framework bus number */
		.chip_select = 3, /* Framework chip select */
		.mode = SPI_MODE_3,
	},
#endif
};
</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>

===== Devicetree =====

Required devicetree properties:
  * compatible: Needs to be "adi," followed by the name of the device. E.g. "adi,ad7476a"
  * reg: The chipselect number used for the device
  * spi-max-frequency: Maximum SPI clock frequency.
  * spi-cpha: Needs to be set for the correct SPI mode
  * spi-cpol: Needs to be set for the correct SPI mode
  * vcc-supply: Phandle to the supply regulator

<code>
       adc_supply: fixedregulator {
               compatible = "regulator-fixed";
               regulator-name = "fixed-supply";
               regulator-min-microvolt = <3300000>;
               regulator-max-microvolt = <3300000>;
       };

       spi: spi@e0007000 {
               #address-cells = <1>;
               #size-cells = <0>;
               compatible = "xlnx,ps7-spi-1.00.a";
               ...

               ad7476@0 {
                       compatible = "adi,ad7476a";
                       reg = <0>;
                       spi-max-frequency = <1000000>;
                       spi-cpha;
                       spi-cpol;
                       vcc-supply = <&adc_supply>;
               };
        };
</code>
====== Adding Linux driver support ======

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

<WRAP round help>
The AD7476 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 AD7476 and similar 1-channel ADCs driver
                ...
            ...
        ...
</code>

====== Hardware configuration ======


====== 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
device0                  device0:buffer0:access0  trigger0
device0:buffer0          device0:buffer0:event0

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

root:/sys/devices/platform/bfin-spi.0/spi0.3/device0> **ls -l**
drwxr-xr-x    5 root     root             0 Jan  1 00:00 buffer
-r--r--r--    1 root     root          4096 Jan  1 00:00 in_voltage0_raw
-r--r--r--    1 root     root          4096 Jan  1 00:00 in_voltage_scale
-r--r--r--    1 root     root          4096 Jan  1 00:00 name
lrwxrwxrwx    1 root     root             0 Jan  1 00:00 subsystem -> ../../../../../bus/iio
drwxr-xr-x    2 root     root             0 Jan  1 00:00 trigger
-rw-r--r--    1 root     root          4096 Jan  1 00:00 uevent
</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/device0> **cat name**
ad7476
</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/devices/platform/bfin-spi.0/spi0.3/device0> **cat in_voltage_scale**
0.805
</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/devices/platform/bfin-spi.0/spi0.3/device0> **cat in_voltage0_raw**
2001
</xterm></WRAP>

**U** = //in_voltage0_raw * in_voltage_scale// = 2001 * 0.805 = **1610,805 //mV//**

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

{{page>software:linux:docs:iio:iio_snippets#iio devices with trigger consumer interface&noheader&firstseconly&noeditbtn}}

==== Available standalone trigger drivers ====

{{page>software:linux:docs:iio:iio_snippets#Standalone trigger drivers&noheader&firstseconly&noeditbtn}}

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

<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/device0:buffer0> ls
**bytes_per_datum**          **enable**                   subsystem
device0:buffer0:access0  **length**                   uevent
device0:buffer0:event0   **scan_elements**
root:/sys/devices/platform/bfin-spi.0/spi0.3/device0/device0:buffer0>
</xterm></WRAP>

{{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/device0/device0:buffer0/scan_elements> ls
in0_en           in_type          timestamp_index
in0_index        timestamp_en     timestamp_type
root:/sys/devices/platform/bfin-spi.0/spi0.3/device0/device0:buffer0/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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