From 0a19f129d71f18e73249d54de96c835186b8607e Mon Sep 17 00:00:00 2001 From: Ben Sen <0.x29a.0@gmail.com> Date: Sun, 1 May 2016 23:23:33 +0200 Subject: w1: add ability to set (SRAM) and store (EEPROM) configuration for temp sensors like DS18B20 Since many temperature sensors come "preconfigured" with a lower precision, people are stuck at that precision when running on a kernel based device (unlike the Dallas 1Wire library for e.g. Arduino, which supports writing the configuration/scratchpad). This patch adds write support for the scratchpad/precision registers via w1_slave sysfs. Signed-off-by: Ben Sen <0.x29a.0@gmail.com> Acked-by: Evgeniy Polyakov Signed-off-by: Greg Kroah-Hartman --- Documentation/w1/slaves/w1_therm | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) (limited to 'Documentation/w1/slaves') diff --git a/Documentation/w1/slaves/w1_therm b/Documentation/w1/slaves/w1_therm index 13411fe52f7f..d1f93af36f38 100644 --- a/Documentation/w1/slaves/w1_therm +++ b/Documentation/w1/slaves/w1_therm @@ -33,7 +33,15 @@ 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). +precision (which would also reduce the conversion time) when reading values. + +Writing a value between 9 and 12 to the sysfs w1_slave file will change the +precision of the sensor for the next readings. This value is in (volatile) +SRAM, so it is reset when the sensor gets power-cycled. + +To store the current precision configuration into EEPROM, the value 0 +has to be written to the sysfs w1_slave file. Since the EEPROM has a limited +amount of writes (>50k), this command should be used wisely. The module parameter strong_pullup can be set to 0 to disable the strong pullup, 1 to enable autodetection or 2 to force strong pullup. -- cgit v1.2.3-59-g8ed1b