According to the documentation for w1-therm:
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.
I can read the w1_slave file(s) easily enough:
pi@xenon:~$ cat /sys/bus/w1/devices/28*/w1_slave a0 01 80 80 1f ff 80 80 f5 : crc=f5 YES a0 01 80 80 1f ff 80 80 f5 t=26000
But I haven't yet figured out how to write them:
pi@xenon:~$ sudo echo 12 >/sys/bus/w1/devices/28-0315549b98ff/w1_slave -bash: /sys/bus/w1/devices/28-0315549b98ff/w1_slave: Permission denied
Any insight into how to make this work.