forked from luck/tmp_suning_uos_patched
8c14d126ae
The LM73 supports four A/D conversion resolutions. The default used by the existing lm73 driver is the chip's default, 11-bit (0.25 C/LSB). This patch enables changing of this resolution from userspace via the update_interval sysfs attribute. Full details on usage are included in Documentation/hwmon/lm73. Signed-off-by: Chris Verges <kg4ysn@gmail.com> [linux@roeck-us.net: cleanup] Signed-off-by: Guenter Roeck <linux@roeck-us.net>
80 lines
2.3 KiB
Plaintext
80 lines
2.3 KiB
Plaintext
Kernel driver lm73
|
|
==================
|
|
|
|
Supported chips:
|
|
* Texas Instruments LM73
|
|
Prefix: 'lm73'
|
|
Addresses scanned: I2C 0x48, 0x49, 0x4a, 0x4c, 0x4d, and 0x4e
|
|
Datasheet: Publicly available at the Texas Instruments website
|
|
http://www.ti.com/product/lm73
|
|
|
|
Author: Guillaume Ligneul <guillaume.ligneul@gmail.com>
|
|
Documentation: Chris Verges <kg4ysn@gmail.com>
|
|
|
|
|
|
Description
|
|
-----------
|
|
|
|
The LM73 is a digital temperature sensor. All temperature values are
|
|
given in degrees Celsius.
|
|
|
|
Measurement Resolution Support
|
|
------------------------------
|
|
|
|
The LM73 supports four resolutions, defined in terms of degrees C per
|
|
LSB: 0.25, 0.125, 0.0625, and 0.3125. Changing the resolution mode
|
|
affects the conversion time of the LM73's analog-to-digital converter.
|
|
From userspace, the desired resolution can be specified as a function of
|
|
conversion time via the 'update_interval' sysfs attribute for the
|
|
device. This attribute will normalize ranges of input values to the
|
|
maximum times defined for the resolution in the datasheet.
|
|
|
|
Resolution Conv. Time Input Range
|
|
(C/LSB) (msec) (msec)
|
|
--------------------------------------
|
|
0.25 14 0..14
|
|
0.125 28 15..28
|
|
0.0625 56 29..56
|
|
0.03125 112 57..infinity
|
|
--------------------------------------
|
|
|
|
The following examples show how the 'update_interval' attribute can be
|
|
used to change the conversion time:
|
|
|
|
$ echo 0 > update_interval
|
|
$ cat update_interval
|
|
14
|
|
$ cat temp1_input
|
|
24250
|
|
|
|
$ echo 22 > update_interval
|
|
$ cat update_interval
|
|
28
|
|
$ cat temp1_input
|
|
24125
|
|
|
|
$ echo 56 > update_interval
|
|
$ cat update_interval
|
|
56
|
|
$ cat temp1_input
|
|
24062
|
|
|
|
$ echo 85 > update_interval
|
|
$ cat update_interval
|
|
112
|
|
$ cat temp1_input
|
|
24031
|
|
|
|
As shown here, the lm73 driver automatically adjusts any user input for
|
|
'update_interval' via a step function. Reading back the
|
|
'update_interval' value after a write operation will confirm the
|
|
conversion time actively in use.
|
|
|
|
Mathematically, the resolution can be derived from the conversion time
|
|
via the following function:
|
|
|
|
g(x) = 0.250 * [log(x/14) / log(2)]
|
|
|
|
where 'x' is the output from 'update_interval' and 'g(x)' is the
|
|
resolution in degrees C per LSB.
|