1*4882a593SmuzhiyunKernel driver w1_ds2438 2*4882a593Smuzhiyun======================= 3*4882a593Smuzhiyun 4*4882a593SmuzhiyunSupported chips: 5*4882a593Smuzhiyun 6*4882a593Smuzhiyun * Maxim DS2438 Smart Battery Monitor 7*4882a593Smuzhiyun 8*4882a593Smuzhiyunsupported family codes: 9*4882a593Smuzhiyun ================ ==== 10*4882a593Smuzhiyun W1_FAMILY_DS2438 0x26 11*4882a593Smuzhiyun ================ ==== 12*4882a593Smuzhiyun 13*4882a593SmuzhiyunAuthor: Mariusz Bialonczyk <manio@skyboo.net> 14*4882a593Smuzhiyun 15*4882a593SmuzhiyunDescription 16*4882a593Smuzhiyun----------- 17*4882a593Smuzhiyun 18*4882a593SmuzhiyunThe DS2438 chip provides several functions that are desirable to carry in 19*4882a593Smuzhiyuna battery pack. It also has a 40 bytes of nonvolatile EEPROM. 20*4882a593SmuzhiyunBecause the ability of temperature, current and voltage measurement, the chip 21*4882a593Smuzhiyunis also often used in weather stations and applications such as: rain gauge, 22*4882a593Smuzhiyunwind speed/direction measuring, humidity sensing, etc. 23*4882a593Smuzhiyun 24*4882a593SmuzhiyunCurrent support is provided through the following sysfs files (all files 25*4882a593Smuzhiyunexcept "iad" are readonly): 26*4882a593Smuzhiyun 27*4882a593Smuzhiyun"iad" 28*4882a593Smuzhiyun----- 29*4882a593SmuzhiyunThis file controls the 'Current A/D Control Bit' (IAD) in the 30*4882a593SmuzhiyunStatus/Configuration Register. 31*4882a593SmuzhiyunWriting a zero value will clear the IAD bit and disables the current 32*4882a593Smuzhiyunmeasurements. 33*4882a593SmuzhiyunWriting value "1" is setting the IAD bit (enables the measurements). 34*4882a593SmuzhiyunThe IAD bit is enabled by default in the DS2438. 35*4882a593Smuzhiyun 36*4882a593SmuzhiyunWhen writing to sysfs file bits 2-7 are ignored, so it's safe to write ASCII. 37*4882a593SmuzhiyunAn I/O error is returned when there is a problem setting the new value. 38*4882a593Smuzhiyun 39*4882a593Smuzhiyun"page0" 40*4882a593Smuzhiyun------- 41*4882a593SmuzhiyunThis file provides full 8 bytes of the chip Page 0 (00h). 42*4882a593SmuzhiyunThis page contains the most frequently accessed information of the DS2438. 43*4882a593SmuzhiyunInternally when this file is read, the additional CRC byte is also obtained 44*4882a593Smuzhiyunfrom the slave device. If it is correct, the 8 bytes page data are passed 45*4882a593Smuzhiyunto userspace, otherwise an I/O error is returned. 46*4882a593Smuzhiyun 47*4882a593Smuzhiyun"temperature" 48*4882a593Smuzhiyun------------- 49*4882a593SmuzhiyunOpening and reading this file initiates the CONVERT_T (temperature conversion) 50*4882a593Smuzhiyuncommand of the chip, afterwards the temperature is read from the device 51*4882a593Smuzhiyunregisters and provided as an ASCII decimal value. 52*4882a593Smuzhiyun 53*4882a593SmuzhiyunImportant: The returned value has to be divided by 256 to get a real 54*4882a593Smuzhiyuntemperature in degrees Celsius. 55*4882a593Smuzhiyun 56*4882a593Smuzhiyun"vad", "vdd" 57*4882a593Smuzhiyun------------ 58*4882a593SmuzhiyunOpening and reading this file initiates the CONVERT_V (voltage conversion) 59*4882a593Smuzhiyuncommand of the chip. 60*4882a593Smuzhiyun 61*4882a593SmuzhiyunDepending on a sysfs filename a different input for the A/D will be selected: 62*4882a593Smuzhiyun 63*4882a593Smuzhiyunvad: 64*4882a593Smuzhiyun general purpose A/D input (VAD) 65*4882a593Smuzhiyunvdd: 66*4882a593Smuzhiyun battery input (VDD) 67*4882a593Smuzhiyun 68*4882a593SmuzhiyunAfter the voltage conversion the value is returned as decimal ASCII. 69*4882a593SmuzhiyunNote: To get a volts the value has to be divided by 100. 70