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Userspace access to IIO
Example, ST Microelectronics LIS3L02DQ accelerometer.
Typical sysfs entries (pruned for clarity)
/sys/class/iio
device0 - iio_dev related elements
name - driver specific identifier (here lis3l02dq)
accel_x - polled (or from ring) raw readout of acceleration
accel_x_gain - hardware gain (calibration)
accel_x_offset - hardware offset (calibration)
available_sampling_frequency
available_sampling_frequency - what options are there
sampling_frequency - control of internal sampling frequency
scan_elements - controls which channels will be stored in the ring buffer
scan_en_accel_x
scan_en_accel_y
scan_en_timestamp
device - link to underlying hardware device
uevent - udev related element
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
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
ring_buffer0 - ring buffer interface
bps - byptes per sample (read only), dependant on scan element selection
length - (rw) specificy length fo software ring buffer (typically ro in hw case)
ring_enable - turn the ring on. If its the first to be enabled attached to this
trigger will also enable the trigger.
ring_access0
dev - major:minor for ring buffer access chrdev
ring_event_line0
dev - major:minor for ring buffer event chrdev
trigger0 - data ready trigger elements
name - unqiue name of trigger
Udev will create the following entries under /dev by default:
ring_access0 - ring access chrdev
ring_event0 - ring event chrdev
event_line0 - general event chrdev.
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:
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"
The files, lis3l02dqbuffersimple.c and iio_utils.h in this directory provide an example
of how to use the ring buffer and event interfaces.
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