diff options
| author | Len Brown <len.brown@intel.com> | 2008-10-22 23:57:26 -0400 |
|---|---|---|
| committer | Len Brown <len.brown@intel.com> | 2008-10-23 00:11:07 -0400 |
| commit | 057316cc6a5b521b332a1d7ccc871cd60c904c74 (patch) | |
| tree | 4333e608da237c73ff69b10878025cca96dcb4c8 /Documentation/w1/slaves/w1_therm | |
| parent | 3e2dab9a1c2deb03c311eb3f83466009147ed4d3 (diff) | |
| parent | 2515ddc6db8eb49a79f0fe5e67ff09ac7c81eab4 (diff) | |
Merge branch 'linus' into test
Conflicts:
MAINTAINERS
arch/x86/kernel/acpi/boot.c
arch/x86/kernel/acpi/sleep.c
drivers/acpi/Kconfig
drivers/pnp/Makefile
drivers/pnp/quirks.c
Signed-off-by: Len Brown <len.brown@intel.com>
Diffstat (limited to 'Documentation/w1/slaves/w1_therm')
| -rw-r--r-- | Documentation/w1/slaves/w1_therm | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/Documentation/w1/slaves/w1_therm b/Documentation/w1/slaves/w1_therm new file mode 100644 index 00000000000..0403aaaba87 --- /dev/null +++ b/Documentation/w1/slaves/w1_therm @@ -0,0 +1,41 @@ +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. |