This version (20 Nov 2015 17:27) was approved by Lars-Peter Clausen.The Previously approved version (11 Mar 2015 10:14) is available.
Table of Contents
ADXRS450 IIO Gyroscope Linux Driver
Supported Devices
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
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.rst
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
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.
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
- IIO mailing list: linux [dash] iio [at] vger [dot] kernel [dot] org
resources/tools-software/linux-drivers/iio-gyroscope/adxrs450.txt · Last modified: 20 Nov 2015 17:27 by Lars-Peter Clausen