w1_ds28e17.rst (2502B)
1======================== 2Kernel driver w1_ds28e17 3======================== 4 5Supported chips: 6 7 * Maxim DS28E17 1-Wire-to-I2C Master Bridge 8 9supported family codes: 10 11 ================= ==== 12 W1_FAMILY_DS28E17 0x19 13 ================= ==== 14 15Author: Jan Kandziora <jjj@gmx.de> 16 17 18Description 19----------- 20The DS28E17 is a Onewire slave device which acts as an I2C bus master. 21 22This driver creates a new I2C bus for any DS28E17 device detected. I2C buses 23come and go as the DS28E17 devices come and go. I2C slave devices connected to 24a DS28E17 can be accessed by the kernel or userspace tools as if they were 25connected to a "native" I2C bus master. 26 27 28An udev rule like the following:: 29 30 SUBSYSTEM=="i2c-dev", KERNEL=="i2c-[0-9]*", ATTRS{name}=="w1-19-*", \ 31 SYMLINK+="i2c-$attr{name}" 32 33may be used to create stable /dev/i2c- entries based on the unique id of the 34DS28E17 chip. 35 36 37Driver parameters are: 38 39speed: 40 This sets up the default I2C speed a DS28E17 get configured for as soon 41 it is connected. The power-on default of the DS28E17 is 400kBaud, but 42 chips may come and go on the Onewire bus without being de-powered and 43 as soon the "w1_ds28e17" driver notices a freshly connected, or 44 reconnected DS28E17 device on the Onewire bus, it will re-apply this 45 setting. 46 47 Valid values are 100, 400, 900 [kBaud]. Any other value means to leave 48 alone the current DS28E17 setting on detect. The default value is 100. 49 50stretch: 51 This sets up the default stretch value used for freshly connected 52 DS28E17 devices. It is a multiplier used on the calculation of the busy 53 wait time for an I2C transfer. This is to account for I2C slave devices 54 which make heavy use of the I2C clock stretching feature and thus, the 55 needed timeout cannot be pre-calculated correctly. As the w1_ds28e17 56 driver checks the DS28E17's busy flag in a loop after the precalculated 57 wait time, it should be hardly needed to tweak this setting. 58 59 Leave it at 1 unless you get ETIMEDOUT errors and a "w1_slave_driver 60 19-00000002dbd8: busy timeout" in the kernel log. 61 62 Valid values are 1 to 9. The default is 1. 63 64 65The driver creates sysfs files /sys/bus/w1/devices/19-<id>/speed and 66/sys/bus/w1/devices/19-<id>/stretch for each device, preloaded with the default 67settings from the driver parameters. They may be changed anytime. In addition a 68directory /sys/bus/w1/devices/19-<id>/i2c-<nnn> for the I2C bus master sysfs 69structure is created. 70 71 72See https://github.com/ianka/w1_ds28e17 for even more information.