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iio: envelope-detector: ADC driver based on a DAC and a comparator

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The DAC is used to find the peak level of an alternating voltage input
signal by a binary search using the output of a comparator wired to
an interrupt pin. Like so:
                          _
                         | \
    input +------>-------|+ \
                         |   \
           .-------.     |    }---.
           |       |     |   /    |
           |    dac|-->--|- /     |
           |       |     |_/      |
           |       |              |
           |       |              |
           |    irq|------<-------'
           |       |
           '-------'

Signed-off-by: Peter Rosin <peda@axentia.se>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
This commit is contained in:
Peter Rosin
2016-11-08 12:58:58 +01:00
committed by Jonathan Cameron
parent e778aa142a
commit b475f80b35
5 changed files with 471 additions and 0 deletions
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36
Documentation/ABI/testing/sysfs-bus-iio-adc-envelope-detector Normal file
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What: /sys/bus/iio/devices/iio:deviceX/in_altvoltageY_invert
Date: October 2016
KernelVersion: 4.9
Contact: Peter Rosin <peda@axentia.se>
Description:
The DAC is used to find the peak level of an alternating
voltage input signal by a binary search using the output
of a comparator wired to an interrupt pin. Like so:
_
| \
input +------>-------|+ \
| \
.-------. | }---.
| | | / |
| dac|-->--|- / |
| | |_/ |
| | |
| | |
| irq|------<-------'
| |
'-------'
The boolean invert attribute (0/1) should be set when the
input signal is centered around the maximum value of the
dac instead of zero. The envelope detector will search
from below in this case and will also invert the result.
The edge/level of the interrupt is also switched to its
opposite value.
What: /sys/bus/iio/devices/iio:deviceX/in_altvoltageY_compare_interval
Date: October 2016
KernelVersion: 4.9
Contact: Peter Rosin <peda@axentia.se>
Description:
Number of milliseconds to wait for the comparator in each
step of the binary search for the input peak level. Needs
to relate to the frequency of the input signal.