This version (11 Mar 2015 10:15) was approved by larsc.

ADXRS450 IIO Gyroscope Linux Driver

Supported Devices

Reference Circuits

Evaluation Boards

ADXRS450: ±300°/sec High Vibration Immunity Digital Gyro

ADXRS453: ±300°/sec High Vibration Immunity Digital Gyro

Adding ADXRS450 to the Kernel

To add support for the ADXRS450 to the kernel build system, a few things must be enabled properly for things to work.The configuration is as following:

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

The ADXRS450 Driver depends on CONFIG_SPI

Linux Kernel Configuration
  Device Drivers  --->
        <*>     Industrial I/O support  --->
          <M>   Analog Devices ADXRS450/3 Digital Output Gyroscope SPI driver

Source Code

Status

Source Mainlined?
git Yes

Files

Function File
driver drivers/iio/gyro/adxrs450.c

Example platform device initialization

Below is an example which is used on Blackfin board file.

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
static struct spi_board_info board_spi_board_info[] __initdata = {
#if defined(CONFIG_ADXRS450) \
	|| defined(CONFIG_ADXRS450_MODULE)
	{
		.modalias = "adxrs450",
		.bus_num = 0,
		.chip_select = GPIO_PF10 + MAX_CTRL_CS,	/* GPIO controlled SSEL */
		.max_speed_hz = 2000000,
		.mode = SPI_MODE_0,
	},
#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);

Hardware configuration

 EVAL-ADXRS450

 PmodGYRO2

Driver testing

Module loading

This specifies any shell prompt running on the target

root:/> modprobe adxrs450
adxrs450 spi0.18: The Part ID is 0x5201
adxrs450 spi0.18: The Serial Number is 0xbaf2

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

root:/sys/devices/platform/bfin-spi.0/spi0.18/iio:device0 > ls -l
-r--r--r--    1 root     root          4096 Jan  3 16:24 dev
-rw-r--r--    1 root     root          4096 Jan  3 16:24 in_anglvel_z_calibbias
-rw-r--r--    1 root     root          4096 Jan  3 16:24 in_anglvel_z_quadrature_correction_raw
-r--r--r--    1 root     root          4096 Jan  3 16:24 in_anglvel_z_raw
-rw-r--r--    1 root     root          4096 Jan  3 16:24 in_anglvel_z_scale
-r--r--r--    1 root     root          4096 Jan  3 16:24 in_temp0_raw
-rw-r--r--    1 root     root          4096 Jan  3 16:24 in_temp0_scale
-r--r--r--    1 root     root          4096 Jan  3 16:24 name
drwxr-xr-x    2 root     root             0 Jan  3 16:24 power
lrwxrwxrwx    1 root     root             0 Jan  3 16:24 subsystem -> ../../../../../bus/iio
-rw-r--r--    1 root     root          4096 Jan  3 16:24 uevent

Show device name

This specifies any shell prompt running on the target

root:/sys/devices/platform/bfin-spi.0/spi0.18/iio:device0> cat name
adxrs450

Show angular rate scale

This specifies any shell prompt running on the target

root:/sys/devices/platform/bfin-spi.0/spi0.18/iio:device0> cat in_anglvel_z_scale
0.000218166

Show angular rate

Rotate the device and read angular rate sampling values from sysfs nodes like this:

Rotate in positive direction

This specifies any shell prompt running on the target

root:/sys/devices/platform/bfin-spi.0/spi0.18/iio:device0 > cat in_anglvel_z_raw
42
root:/sys/devices/platform/bfin-spi.0/spi0.18/iio:device0 > cat in_anglvel_z_raw
1456

Rotate in negative direction

This specifies any shell prompt running on the target

root:/sys/devices/platform/bfin-spi.0/spi0.18/iio:device0 > cat in_anglvel_z_raw
-1657
root:/sys/devices/platform/bfin-spi.0/spi0.18/iio:device0 > cat in_anglvel_z_raw
-17215

Show quadrature correction

This attribute is used to read the amount of quadrature error present in the device at a given time.

This specifies any shell prompt running on the target

root:/sys/devices/platform/bfin-spi.0/spi0.18/iio:device0 > cat in_anglvel_z_quadrature_correction_raw
9

Set dynamic null correction

This attribute is used to make small adjustments to the rateout of the device. This 10-bit value allows the user to adjust the static rateout of the device by up to ±6.4°/sec.

This specifies any shell prompt running on the target

root:/sys/devices/platform/bfin-spi.0/spi0.18/iio:device0 > cat in_gyro_z_raw
40

root:/sys/devices/platform/bfin-spi.0/spi0.18/iio:device0 > echo 40 > in_anglvel_z_calibbias

root:/sys/devices/platform/bfin-spi.0/spi0.18/iio:device0 > cat in_anglvel_z_raw
1

Show temperature

This specifies any shell prompt running on the target

root:/sys/devices/platform/bfin-spi.0/spi0.18/iio:device0> cat in_temp0_scale
200
root:/sys/devices/platform/bfin-spi.0/spi0.18/iio:device0> cat in_temp0_raw
105

T = in_temp0_raw * in_temp0_scale = 105 * 200 = 21000 milli degree Celsius

More Information

resources/tools-software/linux-drivers/iio-gyroscope/adxrs450.txt · Last modified: 11 Mar 2015 10:14 by larsc