ADIS16475 driver¶
This driver supports Analog Device’s IMUs on SPI bus.
1. Supported devices¶
Each supported device is a precision, miniature microelectromechanical system (MEMS) inertial measurement unit (IMU) that includes a triaxial gyroscope and a triaxial accelerometer. Each inertial sensor in the IMU device combines with signal conditioning that optimizes dynamic performance. The factory calibration characterizes each sensor for sensitivity, bias, alignment, linear acceleration (gyroscope bias), and point of percussion (accelerometer location). As a result, each sensor has dynamic compensation formulas that provide accurate sensor measurements over a broad set of conditions.
2. Device attributes¶
Accelerometer, gyroscope measurements are always provided. Furthermore, the driver offers the capability to retrieve the delta angle and the delta velocity measurements computed by the device.
The delta angle measurements represent a calculation of angular displacement between each sample update, while the delta velocity measurements represent a calculation of linear velocity change between each sample update.
Finally, temperature data are provided which show a coarse measurement of the temperature inside of the IMU device. This data is most useful for monitoring relative changes in the thermal environment.
The signal chain of each inertial sensor (accelerometers and gyroscopes) includes the application of unique correction formulas, which are derived from extensive characterization of bias, sensitivity, alignment, response to linear acceleration (gyroscopes), and point of percussion (accelerometer location) over a temperature range of −40°C to +85°C, for each ADIS device. These correction formulas are not accessible, but users do have the opportunity to adjust the bias for each sensor individually through the calibbias attribute.
Each IIO device, has a device folder under /sys/bus/iio/devices/iio:deviceX,
where X is the IIO index of the device. Under these folders reside a set of
device files, depending on the characteristics and features of the hardware
device in questions. These files are consistently generalized and documented in
the IIO ABI documentation.
The following tables show the adis16475 related device files, found in the
specific device folder path /sys/bus/iio/devices/iio:deviceX.
3-Axis Accelerometer related device files |
Description |
in_accel_scale |
Scale for the accelerometer channels. |
in_accel_x_calibbias |
Calibration offset for the X-axis accelerometer channel. |
in_accel_x_raw |
Raw X-axis accelerometer channel value. |
in_accel_y_calibbias |
Calibration offset for the Y-axis accelerometer channel. |
in_accel_y_raw |
Raw Y-axis accelerometer channel value. |
in_accel_z_calibbias |
Calibration offset for the Z-axis accelerometer channel. |
in_accel_z_raw |
Raw Z-axis accelerometer channel value. |
in_deltavelocity_scale |
Scale for delta velocity channels. |
in_deltavelocity_x_raw |
Raw X-axis delta velocity channel value. |
in_deltavelocity_y_raw |
Raw Y-axis delta velocity channel value. |
in_deltavelocity_z_raw |
Raw Z-axis delta velocity channel value. |
3-Axis Gyroscope related device files |
Description |
in_anglvel_scale |
Scale for the gyroscope channels. |
in_anglvel_x_calibbias |
Calibration offset for the X-axis gyroscope channel. |
in_anglvel_x_raw |
Raw X-axis gyroscope channel value. |
in_anglvel_y_calibbias |
Calibration offset for the Y-axis gyroscope channel. |
in_anglvel_y_raw |
Raw Y-axis gyroscope channel value. |
in_anglvel_z_calibbias |
Calibration offset for the Z-axis gyroscope channel. |
in_anglvel_z_raw |
Raw Z-axis gyroscope channel value. |
in_deltaangl_scale |
Scale for delta angle channels. |
in_deltaangl_x_raw |
Raw X-axis delta angle channel value. |
in_deltaangl_y_raw |
Raw Y-axis delta angle channel value. |
in_deltaangl_z_raw |
Raw Z-axis delta angle channel value. |
Temperature sensor related files |
Description |
in_temp0_raw |
Raw temperature channel value. |
in_temp0_scale |
Scale for the temperature sensor channel. |
Miscellaneous device files |
Description |
name |
Name of the IIO device. |
sampling_frequency |
Currently selected sample rate. |
filter_low_pass_3db_frequency |
Bandwidth for the accelerometer and gyroscope channels. |
The following table shows the adis16475 related device debug files, found in the
specific device debug folder path /sys/kernel/debug/iio/iio:deviceX.
Debugfs device files |
Description |
serial_number |
The serial number of the chip in hexadecimal format. |
product_id |
Chip specific product id (e.g. 16475, 16500, 16505, etc.). |
flash_count |
The number of flash writes performed on the device. |
firmware_revision |
String containing the firmware revision in the following format ##.##. |
firmware_date |
String containing the firmware date in the following format mm-dd-yyyy. |
Channels processed values¶
A channel value can be read from its _raw attribute. The value returned is the raw value as reported by the devices. To get the processed value of the channel, apply the following formula:
processed value = (_raw + _offset) * _scale
Where _offset and _scale are device attributes. If no _offset attribute is present, simply assume its value is 0.
The adis16475 driver offers data for 5 types of channels, the table below shows the measurement units for the processed value, which are defined by the IIO framework:
Channel type |
Measurement unit |
Acceleration on X, Y, and Z axis |
Meters per Second squared |
Angular velocity on X, Y and Z axis |
Radians per second |
Delta velocity on X. Y, and Z axis |
Meters per Second |
Delta angle on X, Y, and Z axis |
Radians |
Temperature |
Millidegrees Celsius |
Usage examples¶
Show device name:
root:/sys/bus/iio/devices/iio:device0> cat name
adis16505-2
Show accelerometer channels value:
root:/sys/bus/iio/devices/iio:device0> cat in_accel_x_raw
-275924
root:/sys/bus/iio/devices/iio:device0> cat in_accel_y_raw
-30142222
root:/sys/bus/iio/devices/iio:device0> cat in_accel_z_raw
261265769
root:/sys/bus/iio/devices/iio:device0> cat in_accel_scale
0.000000037
X-axis acceleration = in_accel_x_raw * in_accel_scale = −0.010209188 m/s^2
Y-axis acceleration = in_accel_y_raw * in_accel_scale = −1.115262214 m/s^2
Z-axis acceleration = in_accel_z_raw * in_accel_scale = 9.666833453 m/s^2
Show gyroscope channels value:
root:/sys/bus/iio/devices/iio:device0> cat in_anglvel_x_raw
-3324626
root:/sys/bus/iio/devices/iio:device0> cat in_anglvel_y_raw
1336980
root:/sys/bus/iio/devices/iio:device0> cat in_anglvel_z_raw
-602983
root:/sys/bus/iio/devices/iio:device0> cat in_anglvel_scale
0.000000006
X-axis angular velocity = in_anglvel_x_raw * in_anglvel_scale = −0.019947756 rad/s
Y-axis angular velocity = in_anglvel_y_raw * in_anglvel_scale = 0.00802188 rad/s
Z-axis angular velocity = in_anglvel_z_raw * in_anglvel_scale = −0.003617898 rad/s
Set calibration offset for accelerometer channels:
root:/sys/bus/iio/devices/iio:device0> cat in_accel_x_calibbias
0
root:/sys/bus/iio/devices/iio:device0> echo 5000 > in_accel_x_calibbias
root:/sys/bus/iio/devices/iio:device0> cat in_accel_x_calibbias
5000
Set calibration offset for gyroscope channels:
root:/sys/bus/iio/devices/iio:device0> cat in_anglvel_y_calibbias
0
root:/sys/bus/iio/devices/iio:device0> echo -5000 > in_anglvel_y_calibbias
root:/sys/bus/iio/devices/iio:device0> cat in_anglvel_y_calibbias
-5000
Set sampling frequency:
root:/sys/bus/iio/devices/iio:device0> cat sampling_frequency
2000.000000
root:/sys/bus/iio/devices/iio:device0> echo 1000 > sampling_frequency
1000.000000
Set bandwidth for accelerometer and gyroscope:
root:/sys/bus/iio/devices/iio:device0> cat filter_low_pass_3db_frequency
720
root:/sys/bus/iio/devices/iio:device0> echo 360 > filter_low_pass_3db_frequency
root:/sys/bus/iio/devices/iio:device0> cat filter_low_pass_3db_frequency
360
Show serial number:
root:/sys/kernel/debug/iio/iio:device0> cat serial_number
0x04f9
Show product id:
root:/sys/kernel/debug/iio/iio:device0> cat product_id
16505
Show flash count:
root:/sys/kernel/debug/iio/iio:device0> cat flash_count
150
Show firmware revision:
root:/sys/kernel/debug/iio/iio:device0> cat firmware_revision
1.6
Show firmware date:
root:/sys/kernel/debug/iio/iio:device0> cat firmware_date
06-27-2019
3. Device buffers¶
This driver supports IIO buffers.
All devices support retrieving the raw acceleration, gyroscope and temperature measurements using buffers.
The following device families also support retrieving the delta velocity, delta angle and temperature measurements using buffers:
ADIS16477
ADIS16500
ADIS16505
ADIS16507
However, when retrieving acceleration or gyroscope data using buffers, delta readings will not be available and vice versa.
Usage examples¶
Set device trigger in current_trigger, if not already set:
root:/sys/bus/iio/devices/iio:device0> cat trigger/current_trigger
root:/sys/bus/iio/devices/iio:device0> echo adis16505-2-dev0 > trigger/current_trigger
root:/sys/bus/iio/devices/iio:device0> cat trigger/current_trigger
adis16505-2-dev0
Select channels for buffer read:
root:/sys/bus/iio/devices/iio:device0> echo 1 > scan_elements/in_deltavelocity_x_en
root:/sys/bus/iio/devices/iio:device0> echo 1 > scan_elements/in_deltavelocity_y_en
root:/sys/bus/iio/devices/iio:device0> echo 1 > scan_elements/in_deltavelocity_z_en
root:/sys/bus/iio/devices/iio:device0> echo 1 > scan_elements/in_temp0_en
Set the number of samples to be stored in the buffer:
root:/sys/bus/iio/devices/iio:device0> echo 10 > buffer/length
Enable buffer readings:
root:/sys/bus/iio/devices/iio:device0> echo 1 > buffer/enable
Obtain buffered data:
root:/sys/bus/iio/devices/iio:device0> hexdump -C /dev/iio\:device0
...
00001680 01 1f 00 00 ff ff fe ef 00 00 47 bf 00 03 35 55 |..........G...5U|
00001690 01 1f 00 00 ff ff ff d9 00 00 46 f1 00 03 35 35 |..........F...55|
000016a0 01 1f 00 00 ff ff fe fc 00 00 46 cb 00 03 35 7b |..........F...5{|
000016b0 01 1f 00 00 ff ff fe 41 00 00 47 0d 00 03 35 8b |.......A..G...5.|
000016c0 01 1f 00 00 ff ff fe 37 00 00 46 b4 00 03 35 90 |.......7..F...5.|
000016d0 01 1d 00 00 ff ff fe 5a 00 00 45 d7 00 03 36 08 |.......Z..E...6.|
000016e0 01 1b 00 00 ff ff fe fb 00 00 45 e7 00 03 36 60 |..........E...6`|
000016f0 01 1a 00 00 ff ff ff 17 00 00 46 bc 00 03 36 de |..........F...6.|
00001700 01 1a 00 00 ff ff fe 59 00 00 46 d7 00 03 37 b8 |.......Y..F...7.|
00001710 01 1a 00 00 ff ff fe ae 00 00 46 95 00 03 37 ba |..........F...7.|
00001720 01 1a 00 00 ff ff fe c5 00 00 46 63 00 03 37 9f |..........Fc..7.|
00001730 01 1a 00 00 ff ff fe 55 00 00 46 89 00 03 37 c1 |.......U..F...7.|
00001740 01 1a 00 00 ff ff fe 31 00 00 46 aa 00 03 37 f7 |.......1..F...7.|
...
See Documentation/iio/iio_devbuf.rst for more information about how buffered
data is structured.
4. IIO Interfacing Tools¶
Linux Kernel Tools¶
Linux Kernel provides some userspace tools that can be used to retrieve data from IIO sysfs:
lsiio: example application that provides a list of IIO devices and triggers
iio_event_monitor: example application that reads events from an IIO device and prints them
iio_generic_buffer: example application that reads data from buffer
iio_utils: set of APIs, typically used to access sysfs files.
LibIIO¶
LibIIO is a C/C++ library that provides generic access to IIO devices. The library abstracts the low-level details of the hardware, and provides a simple yet complete programming interface that can be used for advanced projects.
For more information about LibIIO, please see: https://github.com/analogdevicesinc/libiio