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Jonathan Cameron
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Greg Kroah-Hartman
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Sep 5, 2010
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Userspace access to IIO | ||
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Example, ST Microelectronics LIS3L02DQ accelerometer. | ||
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Typical sysfs entries (pruned for clarity) | ||
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/sys/class/iio | ||
device0 - iio_dev related elements | ||
name - driver specific identifier (here lis3l02dq) | ||
accel_x_raw - polled (or from ring) raw readout of acceleration | ||
accel_x_offset - offset to be applied to the raw reading | ||
accel_x_scale - scale to be applied to the raw reading and offset | ||
accel_x_calibbias - hardware offset (calibration) | ||
accel_x_calibscale - hardware gain (calibration) | ||
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sampling_frequency_available - what options are there | ||
sampling_frequency - control of internal sampling frequency | ||
device - link to underlying hardware device | ||
uevent - udev related element | ||
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thresh - unified threshold used for detection on all axis | ||
event_line0_sources - which events are enabled | ||
accel_x_high - enable x axis high threshold event | ||
accel_x_low - enable x axis low threshold event | ||
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event_line0 - event interface | ||
dev - major:minor for the chrdev (note major allocation dynamic) | ||
trigger - consumer attachement | ||
current_trigger - name based association with a trigger | ||
device0:buffer0 - ring buffer interface | ||
bytes_per_datum - byptes per complete datum (read only), | ||
dependant on scan element selection | ||
length - (rw) specificy length fo software ring buffer (typically ro in hw case) | ||
enable - turn the ring on. If its the first to be enabled attached to this | ||
trigger will also enable the trigger. | ||
device0:buffer0:access0 | ||
dev - major:minor for ring buffer access chrdev | ||
device0:buffer0:event0 | ||
dev - major:minor for ring buffer event chrdev | ||
scan_elements - controls which channels will be stored in the ring buffer | ||
accel_x_en | ||
accel_y_en | ||
timestamp_en | ||
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trigger0 - data ready trigger elements | ||
name - unqiue name of trigger | ||
The sysfs attributes are documented in sysfs-bus-iio. | ||
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Udev will create the following entries under /dev by default: | ||
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device0:buffer0:access0 - ring access chrdev | ||
device0:buffer0:event0 - ring event chrdev | ||
event_line0 - general event chrdev. | ||
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For the example code we assume the following rules have been used to ensure | ||
unique and consistent naming of these for the lis3l02dq in question: | ||
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KERNEL="ring_event_line*", ID="spi1.0", DRIVER="lis3l02dq", NAME="iio/lis3l02dq_ring_event" | ||
KERNEL="event_line*", ID="spi1.0", DRIVER="lis3l02dq", NAME="iio/lis3l02dq_event" | ||
KERNEL="ring_access*", ID="spi1.0", DRIVER="lis3l02dq", NAME="iio/lis3l02dq_ring_access" | ||
device0:event0 - general event chrdev. | ||
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The files, lis3l02dqbuffersimple.c and iio_utils.h in this directory provide an example | ||
of how to use the ring buffer and event interfaces. |