This version is outdated by a newer approved version.
This version (09 Nov 2011 12:01) is a draft.
Approvals: 0/1
This version (09 Nov 2011 12:01) is a draft.Approvals: 0/1
This is an old revision of the document!
Table of Contents
ADXRS450 IIO Gyroscope Linux Driver
Supported Devices
Reference Circuits
Evaluation Boards
ADXRS450: ±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 --->
[*] Staging drivers --->
<*> Industrial I/O support --->
<M> Analog Devices ADXRS450 Digital Output Gyroscope SPI driver
Source Code
Status
Files
| Function | File |
|---|---|
| driver | drivers/staging/iio/gyro/adxrs450_core.c |
| include | drivers/staging/iio/gyro/adxrs450.h |
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
<box 100% green|shell prompt running on the target>
root:/> modprobe adxrs450 adxrs450: module is from the staging directory, the quality is unknown, you have been warned. adxrs450 spi0.18: The Part ID is 0x5201 adxrs450 spi0.18: The Serial Number is 0xbaf2</box>
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.
<box 100% green|shell prompt running on the target>
root:/> cd /sys/bus/iio/devices/ root:/sys/bus/iio/devices> ls device0 root:/sys/bus/iio/devices> cd device0 root:/sys/devices/platform/bfin-spi.0/spi0.18/device0> ls -l --w------- 1 root root 4096 Jan 1 00:01 gyro_z_calibbias -r--r--r-- 1 root root 4096 Jan 1 00:01 gyro_z_quadrature_correction_raw -r--r--r-- 1 root root 4096 Jan 1 00:01 gyro_z_raw -r--r--r-- 1 root root 4096 Jan 1 00:01 name drwxr-xr-x 2 root root 0 Jan 1 00:01 power lrwxrwxrwx 1 root root 0 Jan 1 00:01 subsystem -> ../../../../../bus/iio -r--r--r-- 1 root root 4096 Jan 1 00:01 temp_raw -rw-r--r-- 1 root root 4096 Jan 1 00:01 uevent</box>
Show device name
<box 100% green|shell prompt running on the target>
root:/sys/devices/platform/bfin-spi.0/spi0.18/device0> cat name adxrs450</box>
Show angular rate
Rotate the device and read angular rate sampling values from sysfs nodes like this:
Rotate in positive direction
<box 100% green|shell prompt running on the target>
root:/sys/devices/platform/bfin-spi.0/spi0.18/device0> cat gyro_z_raw 42 root:/sys/devices/platform/bfin-spi.0/spi0.18/device0> cat gyro_z_raw 1456</box>
Rotate in negative direction
<box 100% green|shell prompt running on the target>
root:/sys/devices/platform/bfin-spi.0/spi0.18/device0> cat gyro_z_raw -1657 root:/sys/devices/platform/bfin-spi.0/spi0.18/device0> cat gyro_z_raw -17215</box>
Show quadrature correction
This attribute is used to read the amount of quadrature error present in the device at a given time.
<box 100% green|shell prompt running on the target>
root:/sys/devices/platform/bfin-spi.0/spi0.18/device0> cat gyro_z_quadrature_correction_raw 9</box>
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.
<box 100% green|shell prompt running on the target>
root:/sys/devices/platform/bfin-spi.0/spi0.18/device0> cat gyro_z_raw 40 root:/sys/devices/platform/bfin-spi.0/spi0.18/device0> echo 40 > gyro_z_calibbias root:/sys/devices/platform/bfin-spi.0/spi0.18/device0> cat gyro_z_raw 1</box>
Show temperature
<box 100% green|shell prompt running on the target>
root:/sys/devices/platform/bfin-spi.0/spi0.18/device0> cat temp_raw 455</box>
More Information
- IIO mailing list: linux [dash] iio [at] vger [dot] kernel [dot] org
resources/tools-software/linux-drivers/iio-gyroscope/adxrs450.1320836511.txt.gz · Last modified: 09 Nov 2011 12:01 (external edit)