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ADIS16260 IIO Programmable Low Power Gyroscope Linux Driver

Supported Devices

Evaluation Boards

Description

This is a Linux industrial I/O (IIO) subsystem driver, targeting serial interface Gyroscopes. 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

Status

Source Mainlined?
git Yes

Files

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

21 Oct 2010 16:10 · Michael Hennerich

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_ADIS16260) \
	|| defined(CONFIG_ADIS16260_MODULE)
	{
		.modalias = "adis16260",
		.max_speed_hz = 1500000,     /* 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_PF4,
	},
#endif
};
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);

Adding Linux driver support

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

The ADIS16260 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

			          *** Digital gyroscope sensors ***
			    [--snip--]

			    <*>   Analog Devices ADIS16260 Digital Gyroscope Sensor SPI driver

			    [--snip--]

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 · Michael Hennerich

This specifies any 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 06:12 buffer
-r--r--r--    1 root     root          4096 Jan  4 06:12 dev
-r--r--r--    1 root     root          4096 Jan  4 06:12 in_angl_x_raw
-rw-r--r--    1 root     root          4096 Jan  4 06:12 in_gyro_x_calibbias
-rw-r--r--    1 root     root          4096 Jan  4 06:12 in_gyro_x_calibscale
-r--r--r--    1 root     root          4096 Jan  4 06:12 in_gyro_x_raw
-rw-r--r--    1 root     root          4096 Jan  4 06:12 in_gyro_x_scale
-rw-r--r--    1 root     root          4096 Jan  4 06:12 in_temp0_offset
-r--r--r--    1 root     root          4096 Jan  4 06:12 in_temp0_raw
-rw-r--r--    1 root     root          4096 Jan  4 06:12 in_temp0_scale
-r--r--r--    1 root     root          4096 Jan  4 06:12 in_voltage0_supply_raw
-rw-r--r--    1 root     root          4096 Jan  4 06:12 in_voltage0_supply_scale
-r--r--r--    1 root     root          4096 Jan  4 06:12 in_voltage1_raw
-rw-r--r--    1 root     root          4096 Jan  4 06:12 in_voltage1_scale
-r--r--r--    1 root     root          4096 Jan  4 06:12 name
drwxr-xr-x    2 root     root             0 Jan  4 06:12 power
--w-------    1 root     root          4096 Jan  4 06:12 reset
-rw-r--r--    1 root     root          4096 Jan  4 06:12 sampling_frequency
-r--r--r--    1 root     root          4096 Jan  4 06:12 sampling_frequency_available
drwxr-xr-x    2 root     root             0 Jan  4 06:12 scan_elements
lrwxrwxrwx    1 root     root             0 Jan  4 06:12 subsystem -> ../../../../../bus/iio
drwxr-xr-x    2 root     root             0 Jan  4 06:12 trigger
-rw-r--r--    1 root     root          4096 Jan  4 06:12 uevent

Show device name

This specifies any shell prompt running on the target

root:/sys/devices/platform/bfin-spi.0/spi0.5/iio:device0> cat name
adis16260

ADIS16260 device attributes

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

Device files
in_angl_x_raw
in_gyro_x_calibbias
in_gyro_x_calibscale
in_gyro_x_raw
in_gyro_x_scale
in_temp0_offset
in_temp0_raw
in_temp0_scale
in_voltage0_supply_raw
in_voltage0_supply_scale
in_voltage1_raw
in_voltage1_scale
name
reset
sampling_frequency
sampling_frequency_available

Trigger management

This driver only supports it's own default trigger source adis16260-dev0

This specifies any shell prompt running on the target

root:/sys/devices/platform/bfin-spi.0/spi0.5/iio:device0> cat trigger/current_trigger
adis16260-dev0

Buffer management

This specifies any 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:

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

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

scan_elements
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 · Michael Hennerich

This specifies any shell prompt running on the target

root:/sys/devices/platform/bfin-spi.0/spi0.5/iio:device0/scan_elements>ls
in_angl_x_en              in_temp0_en               in_voltage0_supply_en
in_angl_x_index           in_temp0_index            in_voltage0_supply_index
in_angl_x_type            in_temp0_type             in_voltage0_supply_type
in_gyro_x_en              in_timestamp_en           in_voltage1_en
in_gyro_x_index           in_timestamp_index        in_voltage1_index
in_gyro_x_type            in_timestamp_type         in_voltage1_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 · Michael Hennerich

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