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Based on kernel version 4.13.3. Page generated on 2017-09-23 13:56 EST.

1	Kernel driver w1_therm
2	====================
4	Supported chips:
5	  * Maxim ds18*20 based temperature sensors.
6	  * Maxim ds1825 based temperature sensors.
8	Author: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
11	Description
12	-----------
14	w1_therm provides basic temperature conversion for ds18*20 devices, and the
15	ds28ea00 device.
16	supported family codes:
17	W1_THERM_DS18S20	0x10
18	W1_THERM_DS1822		0x22
19	W1_THERM_DS18B20	0x28
20	W1_THERM_DS1825		0x3B
21	W1_THERM_DS28EA00	0x42
23	Support is provided through the sysfs w1_slave file.  Each open and
24	read sequence will initiate a temperature conversion then provide two
25	lines of ASCII output.  The first line contains the nine hex bytes
26	read along with a calculated crc value and YES or NO if it matched.
27	If the crc matched the returned values are retained.  The second line
28	displays the retained values along with a temperature in millidegrees
29	Centigrade after t=.
31	Parasite powered devices are limited to one slave performing a
32	temperature conversion at a time.  If none of the devices are parasite
33	powered it would be possible to convert all the devices at the same
34	time and then go back to read individual sensors.  That isn't
35	currently supported.  The driver also doesn't support reduced
36	precision (which would also reduce the conversion time) when reading values.
38	Writing a value between 9 and 12 to the sysfs w1_slave file will change the
39	precision of the sensor for the next readings. This value is in (volatile)
40	SRAM, so it is reset when the sensor gets power-cycled.
42	To store the current precision configuration into EEPROM, the value 0
43	has to be written to the sysfs w1_slave file. Since the EEPROM has a limited
44	amount of writes (>50k), this command should be used wisely.
46	The module parameter strong_pullup can be set to 0 to disable the
47	strong pullup, 1 to enable autodetection or 2 to force strong pullup.
48	In case of autodetection, the driver will use the "READ POWER SUPPLY"
49	command to check if there are pariste powered devices on the bus.
50	If so, it will activate the master's strong pullup.
51	In case the detection of parasite devices using this command fails
52	(seems to be the case with some DS18S20) the strong pullup can
53	be force-enabled.
54	If the strong pullup is enabled, the master's strong pullup will be
55	driven when the conversion is taking place, provided the master driver
56	does support the strong pullup (or it falls back to a pullup
57	resistor).  The DS18b20 temperature sensor specification lists a
58	maximum current draw of 1.5mA and that a 5k pullup resistor is not
59	sufficient.  The strong pullup is designed to provide the additional
60	current required.
62	The DS28EA00 provides an additional two pins for implementing a sequence
63	detection algorithm.  This feature allows you to determine the physical
64	location of the chip in the 1-wire bus without needing pre-existing
65	knowledge of the bus ordering.  Support is provided through the sysfs
66	w1_seq file.  The file will contain a single line with an integer value
67	representing the device index in the bus starting at 0.
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