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DS1921-Thermochron(3)	     One-Wire File System	 DS1921-Thermochron(3)

NAME
       DS1921 -	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]] | address | crc8	| id | locator
       | r_address | r_id | r_locator |	type ]]

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 al-
       ways 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 PROPERTIES
   address
   r_address
       read-only, ascii
       The  entire  64-bit  unique  ID.	Given as upper case hexidecimal	digits
       (0-9A-F).
       address starts with the family code
       r address is the	address	in reverse order, which	is often used in other
       applications and	labeling.

   crc8
       read-only, ascii
       The  8-bit error	correction portion. Uses cyclic	redundancy check. Com-
       puted from the preceding	56 bits	of the unique ID number. Given as  up-
       per case	hexidecimal digits (0-9A-F).

   family
       read-only, ascii
       The  8-bit  family  code. Unique	to each	type of	device.	Given as upper
       case hexidecimal	digits (0-9A-F).

   id
   r_id
       read-only, ascii
       The 48-bit middle portion of the	unique ID number. Does not include the
       family code or CRC. Given as upper case hexidecimal digits (0-9A-F).
       r  id is	the id in reverse order, which is often	used in	other applica-
       tions and labeling.

   locator
   r_locator
       read-only, ascii
       Uses an extension of the	1-wire design from  iButtonLink	 company  that
       associated  1-wire  physical  connections with a	unique 1-wire code. If
       the connection is behind	a Link Locator the locator will	show a	unique
       8-byte number (16 character hexidecimal)	starting with family code FE.
       If  no  Link  Locator is	between	the device and the master, the locator
       field will be all FF.
       r locator is the	locator	in reverse order.

   present (DEPRECATED)
       read-only, yes-no
       Is the device currently present on the 1-wire bus?

   type
       read-only, ascii
       Part name assigned by Dallas Semi. E.g.	DS2401	Alternative  packaging
       (iButton	vs chip) will not be distiguished.

ALARMS
       None.

DESCRIPTION
   1-Wire
       1-wire is a wiring protocol and series of devices designed and manufac-
       tured by	Dallas Semiconductor, Inc. The bus is  a  low-power  low-speed
       low-connector scheme where the data line	can also provide power.

       Each  device  is	 uniquely and unalterably numbered during manufacture.
       There are a wide	variety	of devices, including memory, sensors  (humid-
       ity, temperature, voltage, contact, current), switches, timers and data
       loggers.	More complex devices (like thermocouple	sensors) can be	 built
       with  these  basic devices. There are also 1-wire devices that have en-
       cryption	included.

       The 1-wire scheme uses a	single bus master and multiple slaves  on  the
       same  wire.  The	bus master initiates all communication.	The slaves can
       be individually discovered and addressed	using their unique ID.

       Bus masters come	in a variety of	configurations including serial,  par-
       allel, i2c, network or USB adapters.

   OWFS	design
       OWFS  is	 a  suite of programs that designed to make the	1-wire bus and
       its devices easily accessible. The underlying priciple is to  create  a
       virtual filesystem, with	the unique ID being the	directory, and the in-
       dividual	properties of the device are represented as simple files  that
       can be read and written.

       Details	of  the	 individual slave or master design are hidden behind a
       consistent interface. The goal is to provide an easy set	of tools for a
       software	 designer  to create monitoring	or control applications. There
       are some	performance enhancements in the	implementation,	including data
       caching,	parallel access	to bus masters,	and aggregation	of device com-
       munication. Still the fundemental goal has been ease of use,  flexibil-
       ity and correctness rather than speed.

   DS1921 Thermochron
       The DS1921 (3) is an iButton device with	many intriguing	functions. Es-
       sentially it monitors temperature, giving both a	log of readings, and a
       histogram of temperature	ranges.	The specification is somewhat complex,
       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.

ADDRESSING
       All  1-wire  devices are	factory	assigned a unique 64-bit address. This
       address is of the form:

       Family Code
	      8	bits

       Address
	      48 bits

       CRC    8	bits

       Addressing under	OWFS is	in hexidecimal,	of form:

	      01.123456789ABC

       where 01	is an example 8-bit family code, and 12345678ABC is an example
       48 bit address.

       The  dot	 is  optional,	and the	CRC code can included. If included, it
       must be correct.

DATASHEET
       http://pdfserv.maxim-ic.com/en/ds/DS2438.pdf
       http://pdfserv.maxim-ic.com/en/an/humsensor.pdf

SEE ALSO
   Programs
       owfs (1)	owhttpd	(1) owftpd (1)	owserver  (1)  owdir  (1)  owread  (1)
       owwrite (1) owpresent (1) owtap (1)

   Configuration and testing
       owfs (5)	owtap (1) owmon	(1)

   Language bindings
       owtcl (3) owperl	(3) owcapi (3)

   Clocks
       DS1427  (3)  DS1904(3)  DS1994  (3)  DS2404  (3)	DS2404S	(3) DS2415 (3)
       DS2417 (3)

   ID
       DS2401 (3) DS2411 (3) DS1990A (3)

   Memory
       DS1982 (3) DS1985 (3) DS1986 (3)	 DS1991	 (3)  DS1992  (3)  DS1993  (3)
       DS1995  (3)  DS1996  (3)	 DS2430A  (3) DS2431 (3) DS2433	(3) DS2502 (3)
       DS2506 (3) DS28E04 (3) DS28EC20 (3)

   Switches
       DS2405 (3) DS2406 (3) DS2408 (3)	DS2409 (3) DS2413 (3) DS28EA00 (3)

   Temperature
       DS1822 (3) DS1825 (3) DS1820 (3)	DS18B20	(3)  DS18S20  (3)  DS1920  (3)
       DS1921  (3) DS1821 (3) DS28EA00 (3) DS28E04 (3) EDS0064 (3) EDS0065 (3)
       EDS0066 (3) EDS0067 (3) EDS0068 (3) EDS0071 (3)	EDS0072	 (3)  MAX31826
       (3)

   Humidity
       DS1922 (3) DS2438 (3) EDS0065 (3) EDS0068 (3)

   Voltage
       DS2450 (3)

   Resistance
       DS2890 (3)

   Multifunction (current, voltage, temperature)
       DS2436  (3)  DS2437  (3)	 DS2438	 (3)  DS2751 (3) DS2755	(3) DS2756 (3)
       DS2760 (3) DS2770 (3) DS2780 (3)	DS2781 (3) DS2788 (3) DS2784 (3)

   Counter
       DS2423 (3)

   LCD Screen
       LCD (3) DS2408 (3)

   Crypto
       DS1977 (3)

   Pressure
       DS2406 (3) TAI8570 EDS0066 (3) EDS0068 (3)

   Moisture
       EEEF (3)	DS2438 (3)

AVAILABILITY
       http://www.owfs.org

AUTHOR
       Paul Alfille (paul.alfille@gmail.com)

OWFS Manpage			     2005		 DS1921-Thermochron(3)

NAME | SYNOPSIS | FAMILY CODE | SPECIAL PROPERTIES | STANDARD PROPERTIES | ALARMS | DESCRIPTION | ADDRESSING | DATASHEET | SEE ALSO | AVAILABILITY | AUTHOR

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