ADXRS450
ADXRS450 IIO Gyroscope.
Supported Devices
Evaluation Boards
ADXRS450: ±300°/sec High Vibration Immunity Digital Gyro
The ADXRS450 is a complete angular rate sensor with integrated signal conditioning and an SPI digital interface. It provides superior vibration rejection through a unique quad sensor design that rejects the influence of linear acceleration, enabling accurate rate sensing in harsh environments.
ADXRS453: ±300°/sec High Vibration Immunity Digital Gyro
The ADXRS453 provides the same quad sensor design as the ADXRS450 with enhanced performance specifications. It offers improved bias stability and sensitivity, making it suitable for precision navigation and motion sensing applications requiring high accuracy and vibration immunity.
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)
Note
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 |
Example platform device initialization
Below is an example which is used on Blackfin board file.
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: Overview of Linux kernel SPI support
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
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.
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
root:/sys/devices/platform/bfin-spi.0/spi0.18/iio:device0> cat name
adxrs450
Show angular rate scale
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
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
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.
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.
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
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