mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-11-30 08:26:48 +07:00
42 lines
1.6 KiB
Plaintext
42 lines
1.6 KiB
Plaintext
|
Kernel driver w1_therm
|
||
|
|
====================
|
||
|
|
|
||
|
|
Supported chips:
|
||
|
|
* Maxim ds18*20 based temperature sensors.
|
||
|
|
|
||
|
|
Author: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
|
||
|
|
|
||
|
|
|
||
|
|
Description
|
||
|
|
-----------
|
||
|
|
|
||
|
|
w1_therm provides basic temperature conversion for ds18*20 devices.
|
||
|
|
supported family codes:
|
||
|
|
W1_THERM_DS18S20 0x10
|
||
|
|
W1_THERM_DS1822 0x22
|
||
|
|
W1_THERM_DS18B20 0x28
|
||
|
|
|
||
|
|
Support is provided through the sysfs w1_slave file. Each open and
|
||
|
|
read sequence will initiate a temperature conversion then provide two
|
||
|
|
lines of ASCII output. The first line contains the nine hex bytes
|
||
|
|
read along with a calculated crc value and YES or NO if it matched.
|
||
|
|
If the crc matched the returned values are retained. The second line
|
||
|
|
displays the retained values along with a temperature in millidegrees
|
||
|
|
Centigrade after t=.
|
||
|
|
|
||
|
|
Parasite powered devices are limited to one slave performing a
|
||
|
|
temperature conversion at a time. If none of the devices are parasite
|
||
|
|
powered it would be possible to convert all the devices at the same
|
||
|
|
time and then go back to read individual sensors. That isn't
|
||
|
|
currently supported. The driver also doesn't support reduced
|
||
|
|
precision (which would also reduce the conversion time).
|
||
|
|
|
||
|
|
The module parameter strong_pullup can be set to 0 to disable the
|
||
|
|
strong pullup or 1 to enable. If enabled the 5V strong pullup will be
|
||
|
|
enabled when the conversion is taking place provided the master driver
|
||
|
|
must support the strong pullup (or it falls back to a pullup
|
||
|
|
resistor). The DS18b20 temperature sensor specification lists a
|
||
|
|
maximum current draw of 1.5mA and that a 5k pullup resistor is not
|
||
|
|
sufficient. The strong pullup is designed to provide the additional
|
||
|
|
current required.
|