Merge branch 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs
[sfrench/cifs-2.6.git] / Documentation / ABI / testing / sysfs-bus-iio-adc-envelope-detector
1 What:           /sys/bus/iio/devices/iio:deviceX/in_altvoltageY_invert
2 Date:           October 2016
3 KernelVersion:  4.9
4 Contact:        Peter Rosin <peda@axentia.se>
5 Description:
6                 The DAC is used to find the peak level of an alternating
7                 voltage input signal by a binary search using the output
8                 of a comparator wired to an interrupt pin. Like so:
9                                            _
10                                           | \
11                      input +------>-------|+ \
12                                           |   \
13                             .-------.     |    }---.
14                             |       |     |   /    |
15                             |    dac|-->--|- /     |
16                             |       |     |_/      |
17                             |       |              |
18                             |       |              |
19                             |    irq|------<-------'
20                             |       |
21                             '-------'
22                 The boolean invert attribute (0/1) should be set when the
23                 input signal is centered around the maximum value of the
24                 dac instead of zero. The envelope detector will search
25                 from below in this case and will also invert the result.
26                 The edge/level of the interrupt is also switched to its
27                 opposite value.
28
29 What:           /sys/bus/iio/devices/iio:deviceX/in_altvoltageY_compare_interval
30 Date:           October 2016
31 KernelVersion:  4.9
32 Contact:        Peter Rosin <peda@axentia.se>
33 Description:
34                 Number of milliseconds to wait for the comparator in each
35                 step of the binary search for the input peak level. Needs
36                 to relate to the frequency of the input signal.