What: /sys/bus/w1/devices/.../alarms
Date: May 2020
Contact: Akira Shimahara <[email protected]>
Description:
(RW) read or write TH and TL (Temperature High an Low) alarms.
Values shall be space separated and in the device range
(typical -55 degC to 125 degC), if not values will be trimmed
to device min/max capabilities. Values are integer as they are
stored in a 8bit register in the device. Lowest value is
automatically put to TL. Once set, alarms could be search at
master level, refer to Documentation/w1/w1-generic.rst for
detailed information
Users: any user space application which wants to communicate with
w1_term device
What: /sys/bus/w1/devices/.../eeprom_cmd
Date: May 2020
Contact: Akira Shimahara <[email protected]>
Description:
(WO) writing that file will either trigger a save of the
device data to its embedded EEPROM, either restore data
embedded in device EEPROM. Be aware that devices support
limited EEPROM writing cycles (typical 50k)
* 'save': save device RAM to EEPROM
* 'restore': restore EEPROM data in device RAM
Users: any user space application which wants to communicate with
w1_term device
What: /sys/bus/w1/devices/.../ext_power
Date: May 2020
Contact: Akira Shimahara <[email protected]>
Description:
(RO) return the power status by asking the device
* '0': device parasite powered
* '1': device externally powered
* '-xx': xx is kernel error when reading power status
Users: any user space application which wants to communicate with
w1_term device
What: /sys/bus/w1/devices/.../resolution
Date: May 2020
Contact: Akira Shimahara <[email protected]>
Description:
(RW) get or set the device resolution (on supported devices,
if not, this entry is not present). Note that the resolution
will be changed only in device RAM, so it will be cleared when
power is lost. Trigger a 'save' to EEPROM command to keep
values after power-on. Read or write are :
* '9..14': device resolution in bit
or resolution to set in bit
* '-xx': xx is kernel error when reading the resolution
* Anything else: do nothing
Some DS18B20 clones are fixed in 12-bit resolution, so the
actual resolution is read back from the chip and verified. Error
is reported if the results differ.
Users: any user space application which wants to communicate with
w1_term device
What: /sys/bus/w1/devices/.../temperature
Date: May 2020
Contact: Akira Shimahara <[email protected]>
Description:
(RO) return the temperature in 1/1000 degC.
* If a bulk read has been triggered, it will directly
return the temperature computed when the bulk read
occurred, if available. If not yet available, nothing
is returned (a debug kernel message is sent), you
should retry later on.
* If no bulk read has been triggered, it will trigger
a conversion and send the result. Note that the
conversion duration depend on the resolution (if
device support this feature). It takes 94ms in 9bits
resolution, 750ms for 12bits.
Users: any user space application which wants to communicate with
w1_term device
What: /sys/bus/w1/devices/.../w1_slave
Date: May 2020
Contact: Akira Shimahara <[email protected]>
Description:
(RW) return the temperature in 1/1000 degC.
*read*: return 2 lines with the hexa output data sent on the
bus, return the CRC check and temperature in 1/1000 degC
*write*:
* '0' : save the 2 or 3 bytes to the device EEPROM
(i.e. TH, TL and config register)
* '9..14' : set the device resolution in RAM
(if supported)
* Anything else: do nothing
refer to Documentation/w1/slaves/w1_therm.rst for detailed
information.
Users: any user space application which wants to communicate with
w1_term device
What: /sys/bus/w1/devices/w1_bus_masterXX/therm_bulk_read
Date: May 2020
Contact: Akira Shimahara <[email protected]>
Description:
(RW) trigger a bulk read conversion. read the status
*read*:
* '-1':
conversion in progress on at least 1 sensor
* '1' :
conversion complete but at least one sensor
value has not been read yet
* '0' :
no bulk operation. Reading temperature will
trigger a conversion on each device
*write*:
'trigger': trigger a bulk read on all supporting
devices on the bus
Note that if a bulk read is sent but one sensor is not read
immediately, the next access to temperature on this device
will return the temperature measured at the time of issue
of the bulk read command (not the current temperature).
Users: any user space application which wants to communicate with
w1_term device
What: /sys/bus/w1/devices/.../conv_time
Date: July 2020
Contact: Ivan Zaentsev <[email protected]>
Description:
(RW) Get, set, or measure a temperature conversion time. The
setting remains active until a resolution change. Then it is
reset to default (datasheet) conversion time for a new
resolution.
*read*:
Actual conversion time in milliseconds.
*write*:
* '0':
Set the default conversion time from the datasheet.
* '1':
Measure and set the conversion time. Make a single
temperature conversion, measure an actual value.
Increase it by 20% for temperature range. A new
conversion time can be obtained by reading this
same attribute.
* other positive value:
Set the conversion time in milliseconds.
Users: An application using the w1_term device
What: /sys/bus/w1/devices/.../features
Date: July 2020
Contact: Ivan Zaentsev <[email protected]>
Description:
(RW) Control optional driver settings.
Bit masks to read/write (bitwise OR):
== ============================================================
1 Enable check for conversion success. If byte 6 of
scratchpad memory is 0xC after conversion, and
temperature reads 85.00 (powerup value) or 127.94
(insufficient power) - return a conversion error.
2 Enable poll for conversion completion. Generate read cycles
after the conversion start and wait for 1's. In parasite
power mode this feature is not available.
== ============================================================
*read*:
Currently selected features.
*write*:
Select features.
Users: An application using the w1_term device
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