summaryrefslogtreecommitdiffstats
path: root/Documentation/w1/slaves/w1_ds28e17.rst
diff options
context:
space:
mode:
Diffstat (limited to 'Documentation/w1/slaves/w1_ds28e17.rst')
-rw-r--r--Documentation/w1/slaves/w1_ds28e17.rst72
1 files changed, 72 insertions, 0 deletions
diff --git a/Documentation/w1/slaves/w1_ds28e17.rst b/Documentation/w1/slaves/w1_ds28e17.rst
new file mode 100644
index 000000000..e2d9f96d8
--- /dev/null
+++ b/Documentation/w1/slaves/w1_ds28e17.rst
@@ -0,0 +1,72 @@
+========================
+Kernel driver w1_ds28e17
+========================
+
+Supported chips:
+
+ * Maxim DS28E17 1-Wire-to-I2C Master Bridge
+
+supported family codes:
+
+ ================= ====
+ W1_FAMILY_DS28E17 0x19
+ ================= ====
+
+Author: Jan Kandziora <jjj@gmx.de>
+
+
+Description
+-----------
+The DS28E17 is a Onewire slave device which acts as an I2C bus master.
+
+This driver creates a new I2C bus for any DS28E17 device detected. I2C buses
+come and go as the DS28E17 devices come and go. I2C slave devices connected to
+a DS28E17 can be accessed by the kernel or userspace tools as if they were
+connected to a "native" I2C bus master.
+
+
+An udev rule like the following::
+
+ SUBSYSTEM=="i2c-dev", KERNEL=="i2c-[0-9]*", ATTRS{name}=="w1-19-*", \
+ SYMLINK+="i2c-$attr{name}"
+
+may be used to create stable /dev/i2c- entries based on the unique id of the
+DS28E17 chip.
+
+
+Driver parameters are:
+
+speed:
+ This sets up the default I2C speed a DS28E17 get configured for as soon
+ it is connected. The power-on default of the DS28E17 is 400kBaud, but
+ chips may come and go on the Onewire bus without being de-powered and
+ as soon the "w1_ds28e17" driver notices a freshly connected, or
+ reconnected DS28E17 device on the Onewire bus, it will re-apply this
+ setting.
+
+ Valid values are 100, 400, 900 [kBaud]. Any other value means to leave
+ alone the current DS28E17 setting on detect. The default value is 100.
+
+stretch:
+ This sets up the default stretch value used for freshly connected
+ DS28E17 devices. It is a multiplier used on the calculation of the busy
+ wait time for an I2C transfer. This is to account for I2C slave devices
+ which make heavy use of the I2C clock stretching feature and thus, the
+ needed timeout cannot be pre-calculated correctly. As the w1_ds28e17
+ driver checks the DS28E17's busy flag in a loop after the precalculated
+ wait time, it should be hardly needed to tweak this setting.
+
+ Leave it at 1 unless you get ETIMEDOUT errors and a "w1_slave_driver
+ 19-00000002dbd8: busy timeout" in the kernel log.
+
+ Valid values are 1 to 9. The default is 1.
+
+
+The driver creates sysfs files /sys/bus/w1/devices/19-<id>/speed and
+/sys/bus/w1/devices/19-<id>/stretch for each device, preloaded with the default
+settings from the driver parameters. They may be changed anytime. In addition a
+directory /sys/bus/w1/devices/19-<id>/i2c-<nnn> for the I2C bus master sysfs
+structure is created.
+
+
+See https://github.com/ianka/w1_ds28e17 for even more information.