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Diffstat (limited to 'Documentation/w1/slaves')
-rw-r--r-- | Documentation/w1/slaves/00-INDEX | 4 | ||||
-rw-r--r-- | Documentation/w1/slaves/w1_therm | 41 |
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diff --git a/Documentation/w1/slaves/00-INDEX b/Documentation/w1/slaves/00-INDEX new file mode 100644 index 000000000000..f8101d6b07b7 --- /dev/null +++ b/Documentation/w1/slaves/00-INDEX | |||
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1 | 00-INDEX | ||
2 | - This file | ||
3 | w1_therm | ||
4 | - The Maxim/Dallas Semiconductor ds18*20 temperature sensor. | ||
diff --git a/Documentation/w1/slaves/w1_therm b/Documentation/w1/slaves/w1_therm new file mode 100644 index 000000000000..0403aaaba878 --- /dev/null +++ b/Documentation/w1/slaves/w1_therm | |||
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1 | Kernel driver w1_therm | ||
2 | ==================== | ||
3 | |||
4 | Supported chips: | ||
5 | * Maxim ds18*20 based temperature sensors. | ||
6 | |||
7 | Author: Evgeniy Polyakov <johnpol@2ka.mipt.ru> | ||
8 | |||
9 | |||
10 | Description | ||
11 | ----------- | ||
12 | |||
13 | w1_therm provides basic temperature conversion for ds18*20 devices. | ||
14 | supported family codes: | ||
15 | W1_THERM_DS18S20 0x10 | ||
16 | W1_THERM_DS1822 0x22 | ||
17 | W1_THERM_DS18B20 0x28 | ||
18 | |||
19 | Support is provided through the sysfs w1_slave file. Each open and | ||
20 | read sequence will initiate a temperature conversion then provide two | ||
21 | lines of ASCII output. The first line contains the nine hex bytes | ||
22 | read along with a calculated crc value and YES or NO if it matched. | ||
23 | If the crc matched the returned values are retained. The second line | ||
24 | displays the retained values along with a temperature in millidegrees | ||
25 | Centigrade after t=. | ||
26 | |||
27 | Parasite powered devices are limited to one slave performing a | ||
28 | temperature conversion at a time. If none of the devices are parasite | ||
29 | powered it would be possible to convert all the devices at the same | ||
30 | time and then go back to read individual sensors. That isn't | ||
31 | currently supported. The driver also doesn't support reduced | ||
32 | precision (which would also reduce the conversion time). | ||
33 | |||
34 | The module parameter strong_pullup can be set to 0 to disable the | ||
35 | strong pullup or 1 to enable. If enabled the 5V strong pullup will be | ||
36 | enabled when the conversion is taking place provided the master driver | ||
37 | must support the strong pullup (or it falls back to a pullup | ||
38 | resistor). The DS18b20 temperature sensor specification lists a | ||
39 | maximum current draw of 1.5mA and that a 5k pullup resistor is not | ||
40 | sufficient. The strong pullup is designed to provide the additional | ||
41 | current required. | ||