'\"
'\" Copyright (c) 2003-2004 Paul H Alfille, MD
'\" (paul.alfille@gmail.com)
'\"
'\" Device manual page for the OWFS -- 1-wire filesystem package
'\" Based on Dallas Semiconductor, Inc's datasheets, and trial and error.
'\"
'\" Free for all use. No warranty. None. Use at your own risk.
'\"
.TH DS1921-Thermochron 3  2005 "OWFS Manpage" "One-Wire File System"
.SH NAME
.B DS1921
\- Thermochron temperature logging iButton.
.SH SYNOPSIS
Temperature logging iButton.
.PP
.B 21
[.]XXXXXXXXXXXX[XX][/[
.br
.B about/[measuring| resolution| samples| templow| temphigh| version]
|
.br
.B clock/[date| running| udate]
|
.br
.B histotgram/[counts[0-62|ALL]| gap| temperature[counts[0-62|ALL]]
|
.br
.B log[date[0-2047|ALL]| elements| temperature[0-2047|ALL]| udate[0-2047|ALL]]
|
.br
.B memory
|
.br
.B mission/[date| delay| easystart| frequency| rollover| running| samples| sampling| udate]
|
.br
.B overtemp/[date[0-11|ALL]| elements| end[0-11|ALL]| count[0-11|ALL]| temperature[0-11|ALL]| udate[0-11|ALL]]
|
.br
.B pages/page.[0-15|ALL]
|
.br
.B temperature
|
.br
.B undertemp/[date[0-11|ALL]| elements|end[0-11|ALL]| count[0-11|ALL]| temperature[0-11|ALL]| udate[0-11|ALL]]
|
'\"
'\" Copyright (c) 2003-2004 Paul H Alfille, MD
'\" (paul.alfille@gmail.com)
'\"
'\" Program manual page for the OWFS -- 1-wire filesystem package
'\" Based on Dallas Semiconductor, Inc's datasheets, and trial and error.
'\"
'\" Free for all use. No warranty. None. Use at your own risk.
'\"
.B address
|
.B crc8
|
.B id
|
.B locator
|
.B r_address
|
.B r_id
|
.B r_locator
|
.B type
]]
.SH FAMILY CODE
.PP
.I 21
.SH SPECIAL PROPERTIES
.SS about/measuring
.I read-only, yes-no
.br
Is this
.I DS1921
currently
.I measuring
a temperature?
.SS about/resolution
.I read-only, floating point
.br
What is the
.I resolution
of the temperature measurments (in the current temperature scale).
.SS about/samples
.I read-only, unsigned integer
.br
How many total temperature measurements has this
.I DS1921
performed?
.SS about/temphigh
.I read-only, floating point
.br
Highest temperature this
.I DS1921
can measure (in the current temperature scale).
.SS about/templow
.I read-only, floating point
.br
Lowest temperature this
.I DS1921
can measure (in the current temperature scale).
.SS about/version
.I read-only, ascii
.br
Specific
.I version
of this
.I DS1921.
.SS clock/date
.I read-write, ascii
.br
26 character date representation of the internal time stored in this
.I DS1921.
Increments once per second while
.I clock/running
.br
Setting
.I date
to a null string will put the current system time.
.br
Accepted date formats are:
.br
  Sat[urday] March 12 12:23:59 2001
.br
  Apr[il] 4 9:34:56 2002
.br
  3/23/04 23:34:57
.br
  current locale setting (your system's format)
.SS clock/running
.I read-write, yes-no
.br
Whether the internal clock is running. This can be explicitly set, and is automatically started by
setting
.I clock/date
or
.I clock/udate
or by starting a mission with
.I mission/easystart
or
.I mission/frequency
.PP
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 essential for a mission.
.SS clock/udate
.I read-write, unsigned integer
.br
A numeric representation of
.I clock/date
.br
The number of seconds in UNIX time (since Jan 1, 1970).
.SS histogram/counts.0 ... histogram/counts.62 histogram/counts.ALL
.I read-only, unsigned integer
.br
The number of samples in the current mission whose temperature fell within the
.I histogram/temperature
to
.I histogram/temperature+histogram/gap
range.
.SS histogram/elements
.I read-only, unsigned integer
.br
The number of bins in the histogram. Always 63.
.SS histogram/gap
.I read-only, floating point
.br
The size of the histogram bin. Depends on the Thermochron version (
.I about/version
) and is usually 4 times
.I about/resolution
.PP
Given in the current temperatature scale.
.SS histogram/temperature.0 ... histogram/temperature.62 histogram/temperature.ALL
.I read-only, floating point
.br
Lower limit of the temperature range for the corresponding histogram bin. In the current temperature scale.
.SS log/date.0 ... log/date.2047 log/date.ALL
.I read-only, ascii
.br
Date that the corresponding
.I log/temperature
was taken, in ascii format. (See
.I clock/date
for more on the format).
The number of valid entries is actually
.I log/elements
since the log may not be full.
.PP
.I 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,
.I mission/rollover
determines the Thermochron's behavior.
.PP
If
.I mission/rollover
is false(0), the log will hold the
.B first
2048 samples and
.I log/date.0
will always be the same as
.I mission/date
.PP
If
.I mission/rollover
is true (1) then the log will hold the
.B last
2048 samples and the entries will be shifted down with each new sample.
.PP
Note the
.I OWFS
code "untwists" the rollover behavior. The data will always be a linear array of earliest to latest.
.PP
.I ALL
is the all data elements comma separated.
.SS log/elements
.I read-only, unsigned integer
.br
Number of valid entries in the log.
.I OWFS
offers the full 2048 values in the log memory, but not that many samples may yet have been taken.
.I log/elements
will range from 0 to 2048 and always be less than or equal to
.I mission/samples
.SS log/temperature.0 ... log/temperature.2047 log/temperature.ALL
.I read-write, floating point
.br
The temperature readings (in the current temperature scale) that correspond to the
.I log/date
sample. See
.I log/date
for details on the indexing scheme and rollover behavior.
.SS log/udate.0 ... log/udate.2047 log/udate.ALL
.I read-write, unsigned integer
.br
A numeric representation of
.I log/date
.br
The number of seconds in UNIX time (since Jan 1, 1970).
.SS memory
.I read-write, binary
.br
User available storage space. 512 bytes. Can also be accessed as 16 pages of 32 bytes with the
.I pages/page.x
properties.
.SS overtemp/count.0 ... overtemp/count.11 overtemp/count.ALL
.SS undertemp/count.0 ... undertemp/count.11 undertemp/count.ALL
.I read-only, unsigned integer
.br
Number of sampling periods that the Thermochron stayed out of range during a mission. Each sampling period is
.I mission/frequency
minutes long.
.SS overtemp/end.0 ... overtemp/end.11 overtemp/end.ALL
.SS undertemp/end.0 ... undertemp/end.11 undertemp/end.ALL
.I read-only, ascii
.br
End of time that the Thermochron went out of range during the current mission. See
.I clock/date
for format.
.PP
Each period can be up to 255 samples in length, and span the time
.I overtemp/date
to
.I overtemp/end
( or
.I undertemp/date
to
.I undertemp/end
).
.SS overtemp/date.0 ... overtemp/date.11 overtemp/date.ALL
.SS undertemp/date.0 ... undertemp/date.11 undertemp/date.ALL
.I read-only, ascii
.br
Time that the Thermochron went out of range during the current mission. See
.I clock/date
for format.
.SS overtemp/elements
.SS undertemp/elements
.I read-only, unsigned integer
.br
Number of entries (0 to 12) in the
.I overtemp
or
.I undertemp
array.
.SS overtemp/temperature
.SS undertemp/temperature
.I read-write, floating point
.br
Temperature limit to trigger alarm and error log.
.I overtemp/temperature
gives upper limit and 
.I undertemp/temperature
gives lower limit.
.br
In current temperature scale.
.SS overtemp/udate.0 ... overtemp/udate.11 overtemp/udate.ALL
.SS undertemp/udate.0 ... undertemp/udate.11 undertemp/udate.ALL
.I read-only, unsigned integer
.br
A numeric representation of
.I overtemp/date
or
.I undertemp/date
.br
The number of seconds in UNIX time (since Jan 1, 1970).
.SS pages/page.0 ... pages/page.15 pages/page.ALL
.I read-write, binary
.br
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.
.br
.I ALL
is an aggregate of the pages. Each page is accessed sequentially.
.SS temperature
.I read-only, floating point
.br
Last temperature explicitly requested. Only available when the mission is not in progress. Value returned in in the current temperature scale.
.SH STANDARD PROPERTIES
'\"
'\" Copyright (c) 2003-2004 Paul H Alfille, MD
'\" (paul.alfille@gmail.com)
'\"
'\" Program manual page for the OWFS -- 1-wire filesystem package
'\" Based on Dallas Semiconductor, Inc's datasheets, and trial and error.
'\"
'\" Free for all use. No warranty. None. Use at your own risk.
'\"
.SS address
.SS r_address
.I read-only, ascii
.br
The entire 64-bit unique ID. Given as upper case hexadecimal digits (0-9A-F).
.br
.I address
starts with the
.I family
code
.br
.I r address
is the
.I address
in reverse order, which is often used in other applications and labeling.
.SS crc8
.I read-only, ascii
.br
The 8-bit error correction portion. Uses cyclic redundancy check. Computed from the preceding 56 bits of the unique ID number. Given as upper case hexadecimal digits (0-9A-F).
.SS family
.I read-only, ascii
.br
The 8-bit family code. Unique to each
.I type
of device. Given as upper case hexadecimal digits (0-9A-F).
.SS id
.SS r_id
.I read-only, ascii
.br
The 48-bit middle portion of the unique ID number. Does not include the family code or CRC. Given as upper case hexadecimal digits (0-9A-F).
.br
.I r id
is the
.I id
in reverse order, which is often used in other applications and labeling.
.SS locator
.SS r_locator
.I read-only, ascii
.br
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
.B Link Locator
the
.I locator will show a unique 8-byte number (16 character hexadecimal) starting with family code FE.
.br
If no
.B Link Locator
is between the device and the master, the
.I locator
field will be all FF.
.br
.I r locator
is the
.I locator
in reverse order.
.SS present (DEPRECATED)
.I read-only, yes-no
.br
Is the device currently
.I present
on the 1-wire bus?
.SS type
.I read-only, ascii
.br
Part name assigned by Dallas Semi. E.g.
.I DS2401
Alternative packaging (iButton vs chip) will not be distiguished.
.SH ALARMS
None.
.SH DESCRIPTION
'\"
'\" Copyright (c) 2003-2004 Paul H Alfille, MD
'\" (paul.alfille@gmail.com)
'\"
'\" Program manual page for the OWFS -- 1-wire filesystem package
'\" Based on Dallas Semiconductor, Inc's datasheets, and trial and error.
'\"
'\" Free for all use. No warranty. None. Use at your own risk.
'\"
.SS 1-Wire
.I 1-wire 
is a wiring protocol and series of devices designed and manufactured
by Dallas Semiconductor, Inc. The bus is a low-power low-speed low-connector
scheme where the data line can also provide power.
.PP
Each device is uniquely and unalterably numbered during manufacture. There are a wide variety
of devices, including memory, sensors (humidity, 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 encryption included.
.PP
The 1-wire scheme uses a single 
.I bus master
and multiple
.I slaves
on the same wire. The bus master initiates all communication. The slaves can be 
individually discovered and addressed using their unique ID.
.PP
Bus masters come in a variety of configurations including serial, parallel, i2c, network or USB
adapters.
.SS OWFS design
.I OWFS
is a suite of programs that designed to make the 1-wire bus and its
devices easily accessible. The underlying principle is to create a virtual
filesystem, with the unique ID being the directory, and the individual
properties of the device are represented as simple files that can be read and written.
.PP 
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 communication. Still the fundamental goal has been ease of use, flexibility
and correctness rather than speed.
.SS DS1921 Thermochron
The
.B 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 complex, but OWFS hides many of the implementation details.
.PP
While on a
.I mission
the
.B DS1921 (3)
records temperature readings in a 2048-sample log and adds them to a 62-bin histogram.
.SH ADDRESSING
'\"
'\" Copyright (c) 2003-2004 Paul H Alfille, MD
'\" (paul.alfille@gmail.com)
'\"
'\" Program manual page for the OWFS -- 1-wire filesystem package
'\" Based on Dallas Semiconductor, Inc's datasheets, and trial and error.
'\"
'\" Free for all use. No warranty. None. Use at your own risk.
'\"
All 1-wire devices are factory assigned a unique 64-bit address. This address is of the form:
.TP
.B Family Code
8 bits
.TP
.B Address
48 bits
.TP
.B CRC
8 bits
.IP
.PP
Addressing under OWFS is in hexadecimal, of form:
.IP
.B 01.123456789ABC
.PP
where
.B 01
is an example 8-bit family code, and
.B 12345678ABC
is an example 48 bit address.
.PP
The dot is optional, and the CRC code can included. If included, it must be correct.
.SH DATASHEET
.br
http://pdfserv.maxim-ic.com/en/ds/DS2438.pdf
.br
http://pdfserv.maxim-ic.com/en/an/humsensor.pdf
.SH SEE ALSO
.SS Programs
.B owfs (1) owhttpd (1) owftpd (1) owserver (1)
.B owdir (1) owread (1) owwrite (1) owpresent (1)
.B owtap (1)
.SS Configuration and testing
.B owfs (5) owtap (1) owmon (1)
.SS Language bindings
.B owtcl (3) owperl (3) owcapi (3)
.SS Clocks
.B DS1427 (3) DS1904 (3) DS1994 (3) DS2404 (3) DS2404S (3) DS2415 (3) DS2417 (3)
.SS ID
.B DS2401 (3) DS2411 (3) DS1990A (3)
.SS Memory
.B 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)
.SS Switches
.B DS2405 (3) DS2406 (3) DS2408 (3) DS2409 (3) DS2413 (3) DS28EA00 (3) InfernoEmbedded (3)
.SS Temperature
.B 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)
.SS Humidity
.B DS1922 (3) DS2438 (3) EDS0065 (3) EDS0068 (3)
.SS Voltage
.B DS2450 (3)
.SS Resistance
.B DS2890 (3)
.SS Multifunction (current, voltage, temperature)
.B DS2436 (3) DS2437 (3) DS2438 (3) DS2751 (3) DS2755 (3) DS2756 (3) DS2760 (3) DS2770 (3) DS2780 (3) DS2781 (3) DS2788 (3) DS2784 (3)
.SS Counter
.B DS2423 (3)
.SS LCD Screen
.B LCD (3) DS2408 (3)
.SS Crypto
.B DS1977 (3)
.SS Pressure
.B DS2406 (3) TAI8570 (3) EDS0066 (3) EDS0068 (3)
.SS Moisture
.B EEEF (3) DS2438 (3)
.SH AVAILABILITY
http://www.owfs.org
.SH AUTHOR
Paul Alfille (paul.alfille@gmail.com)