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====== AD7298 IIO Multi-Channel ADC Linux Driver ======

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

  * [[adi>AD7298]]

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

  * [[adi>EVAL-AD7298SDZ]] 
===== 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/ad7298.c|git]] | [[git.linux.org>drivers/iio/adc/ad7298.c|Yes]] |
===== Files =====

^ Function ^ File ^
| driver  | [[git.linux.org>drivers/iio/adc/ad7298.c]] |
| include | [[git.linux.org>include/linux/platform_data/ad7298.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 ad7298_platform_data - Platform data for the ad7298 ADC driver
 * @ext_ref: Whether to use an external reference voltage.
 **/
struct ad7298_platform_data {
    bool ext_ref;
};
</code>

<code c>
static struct ad7298_platform_data ad7298_pdata = {
	.ext_ref = true,
};
</code>

<WRAP tip>
In case platform_data is not present or set to NULL, the driver will use the AD7298 internal reference.
</WRAP>

{{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_AD7298) || \
 	defined(CONFIG_AD7298_MODULE)
	{
		.modalias = "ad7298",
		.max_speed_hz = 1000000,     /* max spi clock (SCK) speed in HZ */
		.bus_num = 0,
		.chip_select = 3, /* CS, change it for your board */
		.controller_data = &spi_ad7298_chip_info,
		.mode = SPI_MODE_1,
	},
#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 AD7298 Driver depends on **CONFIG_SPI**
</WRAP>

<code>
Linux Kernel Configuration
	Device Drivers  --->
		<*>     Industrial I/O support --->
		    --- Industrial I/O support
		    *** Analog to digital converters ***
		    [--snip--]
		    <*>   Analog Devices AD7298 ADC driver
		    [--snip--]

</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 device0:buffer0
-r--r--r--    1 root     root          4096 Jan  1 00:00 in0_raw
-r--r--r--    1 root     root          4096 Jan  1 00:00 in1_raw
-r--r--r--    1 root     root          4096 Jan  1 00:00 in2_raw
-r--r--r--    1 root     root          4096 Jan  1 00:00 in3_raw
-r--r--r--    1 root     root          4096 Jan  1 00:00 in4_raw
-r--r--r--    1 root     root          4096 Jan  1 00:00 in5_raw
-r--r--r--    1 root     root          4096 Jan  1 00:00 in6_raw
-r--r--r--    1 root     root          4096 Jan  1 00:00 in7_raw
-r--r--r--    1 root     root          4096 Jan  1 00:00 in_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
-r--r--r--    1 root     root          4096 Jan  1 00:00 temp0_input
drwxr-xr-x    2 root     root             0 Jan  1 00:00 trigger
-rw-r--r--    1 root     root          4096 Jan  1 00:00 uevent
root:/sys/devices/platform/bfin-spi.0/spi0.3/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/device0> **cat name**
ad7298
</xterm></WRAP>

=== Show internal temperature ===

**Description:**\\
Shows high accuracy band gap temperature sensor temperature in milli degrees Celsius.

<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 temp0_input**
29750
</xterm></WRAP>

**T** = **29.75 //°C//**

=== 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/device0> **cat in_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/device0> **cat in0_raw**
2158
</xterm></WRAP>

**U** = //in0_raw * in_scale// = 2158 * 0.610 = **1316,38 //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           in2_index        in5_en           in7_index
in0_index        in3_en           in5_index        in_type
in1_en           in3_index        in6_en           timestamp_en
in1_index        in4_en           in6_index        timestamp_index
in2_en           in4_index        in7_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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