1Kernel driver w1_therm 2==================== 3 4Supported chips: 5 * Maxim ds18*20 based temperature sensors. 6 7Author: Evgeniy Polyakov <johnpol@2ka.mipt.ru> 8 9 10Description 11----------- 12 13w1_therm provides basic temperature conversion for ds18*20 devices. 14supported family codes: 15W1_THERM_DS18S20 0x10 16W1_THERM_DS1822 0x22 17W1_THERM_DS18B20 0x28 18 19Support is provided through the sysfs w1_slave file. Each open and 20read sequence will initiate a temperature conversion then provide two 21lines of ASCII output. The first line contains the nine hex bytes 22read along with a calculated crc value and YES or NO if it matched. 23If the crc matched the returned values are retained. The second line 24displays the retained values along with a temperature in millidegrees 25Centigrade after t=. 26 27Parasite powered devices are limited to one slave performing a 28temperature conversion at a time. If none of the devices are parasite 29powered it would be possible to convert all the devices at the same 30time and then go back to read individual sensors. That isn't 31currently supported. The driver also doesn't support reduced 32precision (which would also reduce the conversion time). 33 34The module parameter strong_pullup can be set to 0 to disable the 35strong pullup or 1 to enable. If enabled the 5V strong pullup will be 36enabled when the conversion is taking place provided the master driver 37must support the strong pullup (or it falls back to a pullup 38resistor). The DS18b20 temperature sensor specification lists a 39maximum current draw of 1.5mA and that a 5k pullup resistor is not 40sufficient. The strong pullup is designed to provide the additional 41current required. 42