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Diffstat (limited to 'Documentation/w1/slaves/w1_therm')
| -rw-r--r-- | Documentation/w1/slaves/w1_therm | 13 |
1 files changed, 10 insertions, 3 deletions
diff --git a/Documentation/w1/slaves/w1_therm b/Documentation/w1/slaves/w1_therm index 874a8ca93feb..cc62a95e4776 100644 --- a/Documentation/w1/slaves/w1_therm +++ b/Documentation/w1/slaves/w1_therm @@ -34,9 +34,16 @@ 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 +strong pullup, 1 to enable autodetection or 2 to force strong pullup. +In case of autodetection, the driver will use the "READ POWER SUPPLY" +command to check if there are pariste powered devices on the bus. +If so, it will activate the master's strong pullup. +In case the detection of parasite devices using this command fails +(seems to be the case with some DS18S20) the strong pullup can +be force-enabled. +If the strong pullup is enabled, the master's strong pullup will be +driven when the conversion is taking place, provided the master driver +does 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 |