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ADIS16209 IIO Accelerometer and Inclinometer Linux Driver

Supported Devices

Evaluation Boards


This is a Linux industrial I/O (IIO) subsystem driver, targeting serial interface Inclinometer and Accelerometer. 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 IIO for more information.

Source Code


Source Mainlined?
git Yes


Declaring SPI slave devices

Unlike PCI or USB devices, SPI devices are not enumerated at the hardware level. Instead, the software must know which devices are connected on each SPI bus segment, and what slave selects these devices are using. For this reason, the kernel code must instantiate SPI devices explicitly. The most common method is to declare the SPI devices by bus number.

This method is appropriate when the SPI bus is a system bus, as in many embedded systems, wherein each SPI bus has a number which is known in advance. It is thus possible to pre-declare the SPI devices that inhabit this bus. This is done with an array of struct spi_board_info, which is registered by calling spi_register_board_info().

For more information see: Documentation/spi/spi-summary.rst

21 Oct 2010 16:10

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.

static struct spi_board_info board_spi_board_info[] __initdata = {
#if defined(CONFIG_ADIS16209) \
	|| defined(CONFIG_ADIS16209_MODULE)
		.modalias = "adis16209",
		.max_speed_hz = 1000000,     /* max spi clock (SCK) speed in HZ */
		.bus_num = 0,
		.chip_select = 5, /* CS, change it for your board */
		.platform_data = NULL, /* No spi_driver specific config */
		.mode = SPI_MODE_3,
		.irq = IRQ_PF5,
static int __init board_init(void)
	spi_register_board_info(board_spi_board_info, ARRAY_SIZE(board_spi_board_info));
	return 0;

Adding Linux driver support

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

The ADIS16209 Driver depends on CONFIG_SPI
Linux Kernel Configuration
	Device Drivers  --->
		[*] Staging drivers  --->
			<*>     Industrial I/O support --->
			    --- Industrial I/O support
			    -*-   Enable ring buffer support within IIO
			    -*-     Industrial I/O lock free software ring
			    -*-   Enable triggered sampling support

			          *** Accelerometers ***

			    <*>   Analog Devices ADIS16209 Dual-Axis Digital Inclinometer and Accelerometer


Hardware configuration

Driver testing

Each and every IIO device, typically a hardware chip, has a device folder under /sys/bus/iio/devices/iio:deviceX. Where X is the IIO index of the device. Under every of these directory folders reside a set of files, depending on the characteristics and features of the hardware device in question. These files are consistently generalized and documented in the IIO ABI documentation. In order to determine which IIO deviceX corresponds to which hardware device, the user can read the name file /sys/bus/iio/devices/iio:deviceX/name. In case the sequence in which the iio device drivers are loaded/registered is constant, the numbering is constant and may be known in advance.

02 Mar 2011 15:16

<box 100% green|shell prompt running on the target>

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/spi0.5/iio:device0> ls -l
drwxr-xr-x    2 root     root             0 Jan  4 02:58 buffer
-r--r--r--    1 root     root          4096 Jan  4 02:58 dev
-rw-r--r--    1 root     root          4096 Jan  4 02:58 in_accel_x_calibbias
-r--r--r--    1 root     root          4096 Jan  4 02:58 in_accel_x_raw
-rw-r--r--    1 root     root          4096 Jan  4 02:58 in_accel_x_scale
-rw-r--r--    1 root     root          4096 Jan  4 02:58 in_accel_y_calibbias
-r--r--r--    1 root     root          4096 Jan  4 02:58 in_accel_y_raw
-rw-r--r--    1 root     root          4096 Jan  4 02:58 in_accel_y_scale
-r--r--r--    1 root     root          4096 Jan  4 02:58 in_incli_x_raw
-rw-r--r--    1 root     root          4096 Jan  4 02:58 in_incli_x_scale
-r--r--r--    1 root     root          4096 Jan  4 02:58 in_incli_y_raw
-rw-r--r--    1 root     root          4096 Jan  4 02:58 in_incli_y_scale
-r--r--r--    1 root     root          4096 Jan  4 02:58 in_rot0_raw
-rw-r--r--    1 root     root          4096 Jan  4 02:58 in_temp0_offset
-r--r--r--    1 root     root          4096 Jan  4 02:58 in_temp0_raw
-rw-r--r--    1 root     root          4096 Jan  4 02:58 in_temp0_scale
-r--r--r--    1 root     root          4096 Jan  4 02:58 in_voltage0_raw
-rw-r--r--    1 root     root          4096 Jan  4 02:58 in_voltage0_scale
-r--r--r--    1 root     root          4096 Jan  4 02:58 in_voltage1_raw
-rw-r--r--    1 root     root          4096 Jan  4 02:58 in_voltage1_scale
-r--r--r--    1 root     root          4096 Jan  4 02:58 name
drwxr-xr-x    2 root     root             0 Jan  4 02:58 power
--w-------    1 root     root          4096 Jan  4 02:58 reset
drwxr-xr-x    2 root     root             0 Jan  4 02:58 scan_elements
lrwxrwxrwx    1 root     root             0 Jan  4 02:58 subsystem -> ../../../../../bus/iio
drwxr-xr-x    2 root     root             0 Jan  4 02:58 trigger
-rw-r--r--    1 root     root          4096 Jan  4 02:58 uevent

Show device name

<box 100% green|shell prompt running on the target>

root:/sys/devices/platform/bfin-spi.0/spi0.5/iio:device0> cat name

ADIS16209 device attributes

For a detailed description please see: drivers/staging/iio/Documentation/sysfs-bus-iio

Device files

Trigger management

This driver only supports it's own default trigger source adis16209-dev0

<box 100% green|shell prompt running on the target>

root:/sys/devices/platform/bfin-spi.0/spi0.5/iio:device0> cat trigger/current_trigger

Buffer management

<box 100% green|shell prompt running on the target>

root:/sys/devices/platform/bfin-spi.0/spi0.5/iio:device0/buffer> ls
bytes_per_datum  enable           length

The Industrial I/O subsystem provides support for various ring buffer based data acquisition methods. Apart from device specific hardware buffer support, the user can chose between two different software ring buffer implementations. One is the IIO lock free software ring, and the other is based on Linux kfifo. Devices with buffer support feature an additional sub-folder in the /sys/bus/iio/devices/deviceX/ folder hierarchy. Called deviceX:bufferY, where Y defaults to 0, for devices with a single buffer.

Every buffer implementation features a set of files:

Get/set the number of sample sets that may be held by the buffer.

Enables/disables the buffer. This file should be written last, after length and selection of scan elements.

A single positive integer specifying the maximum number of scan elements to wait for. Poll will block until the watermark is reached. Blocking read will wait until the minimum between the requested read amount or the low water mark is available. Non-blocking read will retrieve the available samples from the buffer even if there are less samples then watermark level. This allows the application to block on poll with a timeout and read the available samples after the timeout expires and thus have a maximum delay guarantee.

A read-only value indicating the bytes of data available in the buffer. In the case of an output buffer, this indicates the amount of empty space available to write data to. In the case of an input buffer, this indicates the amount of data available for reading.

Using the high-speed interface. DMA buffers may have an alignment requirement for the buffer length. Newer versions of the kernel will report the alignment requirements associated with a device through the `length_align_bytes` property.

The scan_elements directory contains interfaces for elements that will be captured for a single triggered sample set in the buffer.

02 Mar 2011 15:16

<box 100% green|shell prompt running on the target>

in_accel_x_en       in_incli_x_index    in_rot0_type        in_voltage0_en
in_accel_x_index    in_incli_x_type     in_temp0_en         in_voltage0_index
in_accel_x_type     in_incli_y_en       in_temp0_index      in_voltage0_type
in_accel_y_en       in_incli_y_index    in_temp0_type       in_voltage1_en
in_accel_y_index    in_incli_y_type     in_timestamp_en     in_voltage1_index
in_accel_y_type     in_rot0_en          in_timestamp_index  in_voltage1_type
in_incli_x_en       in_rot0_index       in_timestamp_type

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.

02 Mar 2011 15:16

More Information

resources/tools-software/linux-drivers/iio-accelerometer/adis16209.1353005312.txt.gz · Last modified: 15 Nov 2012 19:48 by Lars-Peter Clausen