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  1. 15 9月, 2013 3 次提交
    • P
      iio: Add tsl4531 ambient light sensor driver · aab9ba7e
      由 Peter Meerwald 提交于 
      driver for the TSL4531 family of 16-bit I2C ambient light
sensors; information is here:
http://www.ams.com/eng/Products/Light-Sensors/Ambient-Light-Sensor-ALS/TSL45315

the chip offers simple lux output

v3 (thanks Lars-Peter Clausen):
* add mutex to when updating integration time
* fix chip ID checking
* code cleanups
v2:
* rename to tsl4351
* use INT_TIME
Signed-off-by: NPeter Meerwald <pmeerw@pmeerw.net>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>
      aab9ba7e
    • P
      iio: adjd_s311: Use INT_TIME channel info · caeac374
      由 Peter Meerwald 提交于 
      Signed-off-by: NPeter Meerwald <pmeerw@pmeerw.net>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>
      caeac374
    • P
      iio: Add INT_TIME (integration time) channel info attribute · 899d90bd
      由 Peter Meerwald 提交于 
      Integration time is in seconds; it controls the measurement
time and influences the gain of a sensor.

There are two typical ways that scaling is implemented in a device:
1) input amplifier,
2) reference to the ADC is changed.
These both result in the accuracy of the ADC varying (by applying its
sampling over a more relevant range).

Integration time is a way of dealing with noise inherent in the analog
sensor itself.  In the case of a light sensor, a mixture of photon noise
and device specific noise.  Photon noise is dealt with by either improving
the efficiency of the sensor, (more photons actually captured) which is not
easily varied dynamically, or by integrating the measurement over a longer
time period.  Note that this can also be thought of as an averaging of a
number of individual samples and is infact sometimes implemented this way.
Altering integration time implies that the duration of a measurement changes,
a fact the device's user may be interested in.

Hence it makes sense to distinguish between integration time and simple
scale. In some devices both types of control are present and whilst they
will have similar effects on the amplitude of the reading, their effect
on the noise of the measurements will differ considerably.

Used by adjd_s311, tsl4531, tcs3472
The following drivers have similar controls (and could be adapted):
* tsl2563 (integration time is controlled via CALIBSCALE among other things)
* tsl2583 (has integration_time device_attr, but driver doesn't use channels yet)
* tsl2x7x (has integration_time attr)
Signed-off-by: NPeter Meerwald <pmeerw@pmeerw.net>
Cc: Jon Brenner <jon.brenner@ams.com>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>
      899d90bd
  3. 14 9月, 2013 14 次提交
  5. 12 9月, 2013 2 次提交
  7. 10 9月, 2013 1 次提交
  9. 08 9月, 2013 20 次提交