DS1921-Thermochron(3) One-Wire File System DS1921-Thermochron(3)NAMEDS1921 - Thermochron temperature logging iButton.
SYNOPSIS
Temperature logging iButton.
21 [.]XXXXXXXXXXXX[XX][/[
about/[measuring| resolution| samples| templow| temphigh| version] |
clock/[date| running| udate] |
histotgram/[counts[0-62|ALL]| gap| temperature[counts[0-62|ALL]] |
log[date[0-2047|ALL]| elements| temperature[0-2047|ALL]|
udate[0-2047|ALL]] |
memory |
mission/[date| delay| easystart| frequency| rollover| running| samples|
sampling| udate] |
overtemp/[date[0-11|ALL]| elements| end[0-11|ALL]| count[0-11|ALL]|
temperature[0-11|ALL]| udate[0-11|ALL]] |
pages/page.[0-15|ALL] |
temperature |
undertemp/[date[0-11|ALL]| elements|end[0-11|ALL]| count[0-11|ALL]|
temperature[0-11|ALL]| udate[0-11|ALL]] | ]]
FAMILY CODE
21
SPECIAL PROPERTIES
about/measuring
read-only, yes-no
Is this DS1921 currently measuring a temperature?
about/resolution
read-only, floating point
What is the resolution of the temperature measurments (in the current
temperature scale).
about/samples
read-only, unsigned integer
How many total temperature measurements has this DS1921 performed?
about/temphigh
read-only, floating point
Highest temperature this DS1921 can measure (in the current temperature
scale).
about/templow
read-only, floating point
Lowest temperature this DS1921 can measure (in the current temperature
scale).
about/version
read-only, ascii
Specific version of this DS1921.
clock/date
read-write, ascii
26 character date representation of the internal time stored in this
DS1921. Increments once per second while clock/running
Setting date to a null string will put the current system time.
Accepted date formats are:
Sat[urday] March 12 12:23:59 2001
Apr[il] 4 9:34:56 2002
3/23/04 23:34:57
current locale setting (your system's format)
clock/running
read-write, yes-no
Whether the internal clock is running. This can be explicitly set, and
is automatically started by setting clock/date or clock/udate or by
starting a mission with mission/easystart or mission/frequency
The main reason to stop the clock is to conserve the internal battery.
The clock cannot be stopped during a mission, and the clock is essen‐
tial for a mission.
clock/udate
read-write, unsigned integer
A numeric representation of clock/date
The number of seconds in UNIX time (since Jan 1, 1970).
histogram/counts.0 ... histogram/counts.62 histogram/counts.ALL
read-only, unsigned integer
The number of samples in the current mission whose temperature fell
within the histogram/temperature to histogram/temperature+histogram/gap
range.
histogram/elements
read-only, unsigned integer
The number of bins in the histogram. Always 63.
histogram/gap
read-only, floating point
The size of the histogram bin. Depends on the Thermochron version (
about/version ) and is usually 4 times about/resolution
Given in the current temperatature scale.
histogram/temperature.0 ... histogram/temperature.62 histogram/tempera‐
ture.ALL
read-only, floating point
Lower limit of the temperature range for the corresponding histogram
bin. In the current temperature scale.
log/date.0 ... log/date.2047 log/date.ALL
read-only, ascii
Date that the corresponding log/temperature was taken, in ascii format.
(See clock/date for more on the format). The number of valid entries
is actually log/elements since the log may not be full.
mission/samples gives the total number of samples that have been taken
but there is only room in the log for 2048 entries. Once the log is
full, mission/rollover determines the Thermochron's behavior.
If mission/rollover is false(0), the log will hold the first 2048 sam‐
ples and log/date.0 will always be the same as mission/date
If mission/rollover is true (1) then the log will hold the last 2048
samples and the entries will be shifted down with each new sample.
Note the OWFS code "untwists" the rollover behavior. The data will
always be a linear array of earliest to latest.
ALL is the all data elements comma separated.
log/elements
read-only, unsigned integer
Number of valid entries in the log. OWFS offers the full 2048 values
in the log memory, but not that many samples may yet have been taken.
log/elements will range from 0 to 2048 and always be less than or equal
to mission/samples
log/temperature.0 ... log/temperature.2047 log/temperature.ALL
read-write, floating point
The temperature readings (in the current temperature scale) that corre‐
spond to the log/date sample. See log/date for details on the indexing
scheme and rollover behavior.
log/udate.0 ... log/udate.2047 log/udate.ALL
read-write, unsigned integer
A numeric representation of log/date
The number of seconds in UNIX time (since Jan 1, 1970).
memory
read-write, binary
User available storage space. 512 bytes. Can also be accessed as 16
pages of 32 bytes with the pages/page.x properties.
overtemp/count.0 ... overtemp/count.11 overtemp/count.ALL
undertemp/count.0 ... undertemp/count.11 undertemp/count.ALL
read-only, unsigned integer
Number of sampling periods that the Thermochron stayed out of range
durring a mission. Each sampling period is mission/frequency minutes
long.
overtemp/end.0 ... overtemp/end.11 overtemp/end.ALL
undertemp/end.0 ... undertemp/end.11 undertemp/end.ALL
read-only, ascii
End of time that the Thermochron went out of range during the current
mission. See clock/date for format.
Each period can be up to 255 samples in length, and span the time
overtemp/date to overtemp/end ( or undertemp/date to undertemp/end ).
overtemp/date.0 ... overtemp/date.11 overtemp/date.ALL
undertemp/date.0 ... undertemp/date.11 undertemp/date.ALL
read-only, ascii
Time that the Thermochron went out of range during the current mission.
See clock/date for format.
overtemp/elements
undertemp/elements
read-only, unsigned integer
Number of entries (0 to 12) in the overtemp or undertemp array.
overtemp/temperature
undertemp/temperature
read-write, floating point
Temperature limit to trigger alarm and error log. overtemp/temperature
gives upper limit and undertemp/temperature gives lower limit.
In current temperature scale.
overtemp/udate.0 ... overtemp/udate.11 overtemp/udate.ALL
undertemp/udate.0 ... undertemp/udate.11 undertemp/udate.ALL
read-only, unsigned integer
A numeric representation of overtemp/date or undertemp/date
The number of seconds in UNIX time (since Jan 1, 1970).
pages/page.0 ... pages/page.15 pages/page.ALL
read-write, binary
Memory is split into 16 pages of 32 bytes each. User available. The log
memory, register banks and histogram data area are all separate from
this memory area.
ALL is an aggregate of the pages. Each page is accessed sequentially.
temperature
read-only, floating point
Last temperature explicitly requested. Only available when the mission
is not in progress. Value returned in in the current temperature scale.
STANDARD PROPERTIESALARMS
None.
DESCRIPTIONDS1921 Thermochron
The DS1921 (3) is an iButton device with many intriguing functions.
Essentially it monitors temperature, giving both a log of readings, and
a histogram of temperature ranges. The specification is somewhat com‐
plex, but OWFS hides many of the implementation details.
While on a mission the DS1921 (3) records temperature readings in a
2048-sample log and adds them to a 62-bin histogram.
ADDRESSINGDATASHEET
http://pdfserv.maxim-ic.com/en/ds/DS2438.pdf
http://pdfserv.maxim-ic.com/en/an/humsensor.pdf
SEE ALSOAVAILABILITY
http://www.owfs.org
AUTHOR
Paul Alfille (paul.alfille@gmail.com)
OWFS Manpage 2005 DS1921-Thermochron(3)
