Kernel driver w1_therm ==================== Supported chips: * Maxim ds18*20 based temperature sensors. Author: Evgeniy Polyakov Description ----------- w1_therm provides basic temperature conversion for ds18*20 devices. supported family codes: W1_THERM_DS18S20 0x10 W1_THERM_DS1822 0x22 W1_THERM_DS18B20 0x28 Support is provided through the sysfs w1_slave file. Each open and read sequence will initiate a temperature conversion then provide two lines of ASCII output. The first line contains the nine hex bytes read along with a calculated crc value and YES or NO if it matched. If the crc matched the returned values are retained. The second line displays the retained values along with a temperature in millidegrees Centigrade after t=. Parasite powered devices are limited to one slave performing a temperature conversion at a time. If none of the devices are parasite powered it would be possible to convert all the devices at the same time and then go back to read individual sensors. That isn't currently supported. The driver also doesn't support reduced precision (which would also reduce the conversion time). The module parameter strong_pullup can be set to 0 to disable the strong pullup or 1 to enable. If enabled the 5V strong pullup will be enabled when the conversion is taking place provided the master driver must support the strong pullup (or it falls back to a pullup resistor). The DS18b20 temperature sensor specification lists a maximum current draw of 1.5mA and that a 5k pullup resistor is not sufficient. The strong pullup is designed to provide the additional current required.