1*4882a593Smuzhiyun======================== 2*4882a593SmuzhiyunKernel driver w1_ds28e17 3*4882a593Smuzhiyun======================== 4*4882a593Smuzhiyun 5*4882a593SmuzhiyunSupported chips: 6*4882a593Smuzhiyun 7*4882a593Smuzhiyun * Maxim DS28E17 1-Wire-to-I2C Master Bridge 8*4882a593Smuzhiyun 9*4882a593Smuzhiyunsupported family codes: 10*4882a593Smuzhiyun 11*4882a593Smuzhiyun ================= ==== 12*4882a593Smuzhiyun W1_FAMILY_DS28E17 0x19 13*4882a593Smuzhiyun ================= ==== 14*4882a593Smuzhiyun 15*4882a593SmuzhiyunAuthor: Jan Kandziora <jjj@gmx.de> 16*4882a593Smuzhiyun 17*4882a593Smuzhiyun 18*4882a593SmuzhiyunDescription 19*4882a593Smuzhiyun----------- 20*4882a593SmuzhiyunThe DS28E17 is a Onewire slave device which acts as an I2C bus master. 21*4882a593Smuzhiyun 22*4882a593SmuzhiyunThis driver creates a new I2C bus for any DS28E17 device detected. I2C buses 23*4882a593Smuzhiyuncome and go as the DS28E17 devices come and go. I2C slave devices connected to 24*4882a593Smuzhiyuna DS28E17 can be accessed by the kernel or userspace tools as if they were 25*4882a593Smuzhiyunconnected to a "native" I2C bus master. 26*4882a593Smuzhiyun 27*4882a593Smuzhiyun 28*4882a593SmuzhiyunAn udev rule like the following:: 29*4882a593Smuzhiyun 30*4882a593Smuzhiyun SUBSYSTEM=="i2c-dev", KERNEL=="i2c-[0-9]*", ATTRS{name}=="w1-19-*", \ 31*4882a593Smuzhiyun SYMLINK+="i2c-$attr{name}" 32*4882a593Smuzhiyun 33*4882a593Smuzhiyunmay be used to create stable /dev/i2c- entries based on the unique id of the 34*4882a593SmuzhiyunDS28E17 chip. 35*4882a593Smuzhiyun 36*4882a593Smuzhiyun 37*4882a593SmuzhiyunDriver parameters are: 38*4882a593Smuzhiyun 39*4882a593Smuzhiyunspeed: 40*4882a593Smuzhiyun This sets up the default I2C speed a DS28E17 get configured for as soon 41*4882a593Smuzhiyun it is connected. The power-on default of the DS28E17 is 400kBaud, but 42*4882a593Smuzhiyun chips may come and go on the Onewire bus without being de-powered and 43*4882a593Smuzhiyun as soon the "w1_ds28e17" driver notices a freshly connected, or 44*4882a593Smuzhiyun reconnected DS28E17 device on the Onewire bus, it will re-apply this 45*4882a593Smuzhiyun setting. 46*4882a593Smuzhiyun 47*4882a593Smuzhiyun Valid values are 100, 400, 900 [kBaud]. Any other value means to leave 48*4882a593Smuzhiyun alone the current DS28E17 setting on detect. The default value is 100. 49*4882a593Smuzhiyun 50*4882a593Smuzhiyunstretch: 51*4882a593Smuzhiyun This sets up the default stretch value used for freshly connected 52*4882a593Smuzhiyun DS28E17 devices. It is a multiplier used on the calculation of the busy 53*4882a593Smuzhiyun wait time for an I2C transfer. This is to account for I2C slave devices 54*4882a593Smuzhiyun which make heavy use of the I2C clock stretching feature and thus, the 55*4882a593Smuzhiyun needed timeout cannot be pre-calculated correctly. As the w1_ds28e17 56*4882a593Smuzhiyun driver checks the DS28E17's busy flag in a loop after the precalculated 57*4882a593Smuzhiyun wait time, it should be hardly needed to tweak this setting. 58*4882a593Smuzhiyun 59*4882a593Smuzhiyun Leave it at 1 unless you get ETIMEDOUT errors and a "w1_slave_driver 60*4882a593Smuzhiyun 19-00000002dbd8: busy timeout" in the kernel log. 61*4882a593Smuzhiyun 62*4882a593Smuzhiyun Valid values are 1 to 9. The default is 1. 63*4882a593Smuzhiyun 64*4882a593Smuzhiyun 65*4882a593SmuzhiyunThe driver creates sysfs files /sys/bus/w1/devices/19-<id>/speed and 66*4882a593Smuzhiyun/sys/bus/w1/devices/19-<id>/stretch for each device, preloaded with the default 67*4882a593Smuzhiyunsettings from the driver parameters. They may be changed anytime. In addition a 68*4882a593Smuzhiyundirectory /sys/bus/w1/devices/19-<id>/i2c-<nnn> for the I2C bus master sysfs 69*4882a593Smuzhiyunstructure is created. 70*4882a593Smuzhiyun 71*4882a593Smuzhiyun 72*4882a593SmuzhiyunSee https://github.com/ianka/w1_ds28e17 for even more information. 73