NAME
am2315temp —
Driver for Aosong AM2315
sensor chip via I2C bus
SYNOPSIS
am2315temp* at iic? addr 0x5c
DESCRIPTION
The
am2315temp driver provides measurements from the AM2315
humidity/temperature sensors via the
envsys(4) framework. The
am2315temp addr argument selects the
address at the
iic(4) bus. The
AM2315 has limits on how often the measurements can be read. Adjustments to
the number of times to take reading before considering it valid, and the
number of ticks to wait between readings can be changed through
sysctl(8) nodes.
There are other oddities about the AM2315 that should be mentioned. The
datasheet says that the device should read no more often then every 2 seconds,
further, it also implies that a measurement is not performed until the device
is 1) awake 2) has been asked for a measurement. From observation, it has been
noted that it is possible to ask for measurements more often than every 2
seconds, and actually get something that looks to be valid. It may, in fact,
be valid, but it has also been noted that the measurements do not appear to
change. This implies that a measurement was done, and then returned time and
time again. It has also been noticed that if measurements are taken very close
to every 2 seconds, that sometimes the device will return a I2C error on a
read. If this happens a lot, increase hw.am2315temp0.readticks a bit.
SYSCTL VARIABLES
The following
sysctl(3) variables
are provided:
-
-
- hw.am2315temp0.readcount
- The number of times to take a reading before considering it
valid. This defaults to 2.
-
-
- hw.am2315temp0.readticks
- The number of ticks to wait in between readings. The
default is 100.
-
-
- hw.am2315temp0.debug
- If the driver is compiled with
AM2315_DEBUG
, this node will appear and can be
used to set the debugging level.
SEE ALSO
envsys(4),
iic(4),
envstat(8),
sysctl(8)
HISTORY
The
am2315temp driver first appeared in
NetBSD 8.0.
AUTHORS
The
am2315temp driver was written by
Brad
Spencer
<
brad@anduin.eldar.org>.
BUGS
The device does not appear to work with the
gpioiic(4) bitbang controller.
When tried, reads would not error, but no data was returned.