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====== AD7887 IIO ADC Linux Driver ======

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

  * [[adi>AD7887]]


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

  * [[adi>CN0150]]
  * [[adi>CN0189]]

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

  * [[adi>EVAL-AD7887CBZ]]

===== Description =====

This is a Linux industrial I/O ([[software:linux:docs:iio:iio|IIO]]) subsystem driver, targeting single/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/ad7887.c|git]] | [[git.linux.org>drivers/iio/adc/ad7887.c|Yes]] |

===== Files =====

^ Function ^ File ^
| driver  | [[git.linux.org>drivers/iio/adc/ad7887.c]] |
| include | [[git.linux.org>include/linux/platform_data/ad7887.h]] |
====== Example platform device initialization ======

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

The reference voltage may vary between boards and models. The platform_data for the device's "struct device" holds this information.

<code c>
/**
 * struct ad7887_platform_data - AD7887 ADC driver platform data
 * @en_dual: Whether to use dual channel mode. If set to true AIN1 becomes the
 *  second input channel, and Vref is internally connected to Vdd. If set to
 *  false the device is used in single channel mode and AIN1/Vref is used as
 *  VREF input.
 * @use_onchip_ref: Whether to use the on-chip reference. If set to true the
 *  internal 2.5V reference is used. If set to false a external reference is
 *  used.
 */
struct ad7887_platform_data {
	bool en_dual;
	bool use_onchip_ref;
};
</code>

<code c>
static struct ad7887_platform_data ad7887_pdata = {
	.en_dual = false,
	.use_onchip_ref = false,
};
</code>
===== Specifying reference voltage via the regulator framework =====

<WRAP tip>
This driver supports also an alternative way of specifying the reference voltage, by using the Linux regulator framework.
</WRAP>

Below example specifies a 2.5 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 ad7887_consumer_supplies[] = {
	REGULATOR_SUPPLY("vcc", "spi0.3"),
};

static struct regulator_init_data stamp_avdd_reg_init_data = {
	.constraints	= {
		.name	= "2V5",
		.valid_ops_mask = REGULATOR_CHANGE_STATUS,
	},
	.consumer_supplies = ad7887_consumer_supplies,
	.num_consumer_supplies = ARRAY_SIZE(ad7887_consumer_supplies),
};

static struct fixed_voltage_config stamp_vdd_pdata = {
	.supply_name	= "board-2V5",
	.microvolts	= 2500000,
	.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_AD7887) || \
 	defined(CONFIG_AD7887_MODULE)
	{
		/* the modalias must be the same as spi device driver name */
		.modalias = "ad7887", /* 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 */
		.platform_data = &ad7887_pdata,
		.controller_data = &ad7887_chip_info, /* Blackfin only */
		.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>

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

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

<WRAP round help>
The AD7887 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 AD7887 ADC 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
iio:device0                  trigger0

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

root:/sys/devices/platform/bfin-spi.0/spi0.3/iio: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/iio:device0> **cat name**
ad7887
</xterm></WRAP>


=== Show scale ===

**Description:**\\
scale to be applied to in0_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/iio:device0> **cat in_voltage_scale**
0.610
</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/iio:device0> **cat in_voltage0_raw**
1492
</xterm></WRAP>

**U** = //in0_raw * in_scale// = 1492 * 0.610 = **910.12 //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/iio:device0/buffer> ls
**enable**                  **length**

</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/iio:device0/scan_elements> ls
in_voltage0_en           in_voltage0_type    timestamp_index
in_voltage0_index        timestamp_en        timestamp_type
</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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