summaryrefslogtreecommitdiff
path: root/Documentation/w1/slaves/w1_therm
diff options
context:
space:
mode:
authorArjan van de Ven <arjan@linux.intel.com>2008-10-17 20:20:26 +0400
committerArjan van de Ven <arjan@linux.intel.com>2008-10-17 20:20:26 +0400
commit651dab4264e4ba0e563f5ff56f748127246e9065 (patch)
tree016630974bdcb00fe529b673f96d389e0fd6dc94 /Documentation/w1/slaves/w1_therm
parent40b8606253552109815786e5d4b0de98782d31f5 (diff)
parent2e532d68a2b3e2aa6b19731501222069735c741c (diff)
downloadlinux-651dab4264e4ba0e563f5ff56f748127246e9065.tar.xz
Merge commit 'linus/master' into merge-linus
Conflicts: arch/x86/kvm/i8254.c
Diffstat (limited to 'Documentation/w1/slaves/w1_therm')
-rw-r--r--Documentation/w1/slaves/w1_therm41
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 000000000000..0403aaaba878
--- /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.