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DS1825(3)		     One-Wire File System		     DS1825(3)

NAME
       DS1825 -	Programmable Resolution	1-Wire Digital Thermometer with	ID

       MAX31826
	      -	Digital	Temperature Sensor with	1Kb Lockable EEPROM

       MAX31850	MAX31851
	      -	Cold-Junction Compensated Thermocouple

SYNOPSIS
   Thermometer with hardware address pins (DS1825)
       3B  [.]XXXXXXXXXXXX[XX][/[ fasttemp | temperature | temperature9	| tem-
       perature10 | temperature11 |  temperature12  |  latesttemp  |  power  |
       prog_addr  | temphigh | templow | tempres | address | crc8 | id | loca-
       tor | r_address | r_id |	r_locator | type ]]

   Digital Temperature Sensor with 1Kb Lockable	EEPROM (MAX31826)
       3B [.]XXXXXXXXXXXX[XX][/[ temperature | latesttemp | power |  memory  |
       pages/page.[0-15|ALL]  |	 prog_addr  |  address | crc8 |	id | locator |
       r_address | r_id	| r_locator | type ]]

   Cold-Junction Compensated Thermocouple (MAX31850 and	MAX31851)
       3B [.]XXXXXXXXXXXX[XX][/[ temperature |	latesttemp  |  thermocouple  |
       fault  |	 open_circuit |	ground_short | vdd_short | power | prog_addr |
       address | crc8 |	id | locator | r_address | r_id	| r_locator | type ]]

FAMILY CODE
       3B

SPECIAL	PROPERTIES
   power
       read-only,yes-no
       Is the chip powered externally (=1) or from the parasitically from  the
       data bus	(=0)?

   prog_addr
       read-only, 0-15
       A  distiguishing	 feature of the	DS1825 (3) is the ability to set hard-
       ware pins for an	address	(0-15).	This is	an alternative to  the	unique
       64-bit address that is set in the factory.

   temperature
       read-only, floating point
       Measured	temperature with 12 bit	resolution.

       For the MAX31850	MAX 31851 this is the cold-junction temperature	-- the
       temperature at the chip.	See thermocouple

   temperature9	temperature10 temperature11 temperature12
       read-only, floating point ( DS1825 only)

       Measured	temperature at 9 to 12 bit resolution. There is	a tradeoff  of
       time versus accuracy in the temperature measurement.

       The  MAX31826  MAX31850	MAX31851  measure  all	temperatures at	12 bit
       resoltion and will return that resolution to all	the possible  tempera-
       ture properties.

   latesttemp
       read-only, floating point
       Measured	 temperature at	9 to 12	bit resolution,	depending on the reso-
       lution of the latest conversion on this chip. Reading  this  node  will
       never trigger a temperature conversion. Intended	for use	in conjunction
       with /simultaneous/temperature.

   fasttemp
       read-only, floating point
       Equivalent to temperature9

   thermocouple
       read-only, floating point ( MAX31850 MAX31851 only)

       Measured	temperature of the thermocouple	 at  16bit  resolution.	 Cold-
       junction	temperature compensated.

       The actual thermocouple type used is set	by the selected	chip type, and
       is not discoverable in software.

TEMPERATURE ALARM LIMITS
       When the	device exceeds either temphigh or templow temperature  thresh-
       old  the	device is in the alarm state, and will appear in the alarm di-
       rectory.	This provides an easy way to poll for  temperatures  that  are
       unsafe, especially if simultaneous temperature conversion is done.

       Units for the temperature alarms	are in the same	temperature scale that
       was set for temperature measurements.

       Temperature thresholds are stored in non-volatile  memory  and  persist
       until changed, even if power is lost.

   temphigh
       read-write, integer
       Shows or	sets the lower limit for the high temperature alarm state.

   templow
       read-write, integer
       Shows or	sets the upper limit for the low temperature alarm state.

       The  MAX31826  does  NOT	 have  temperature  thresholds and temperature
       alarm.

TEMPERATURE RESOLUTION DEFAULT VALUE
   tempres
       read-write, integer
       The device employs a non-volatile memory	to store the default  tempera-
       ture  resolution	 (9,  10, 11 or	12 bits) to be applied after power-up.
       This is useful if you use simultaneous temperature conversions. Reading
       this  node gives	you the	value stored in	the non-volatile memory. Writ-
       ing sets	a new power-on resolution value.

       As a side effect, reading this node resets the  temperature  resolution
       used  by	simultaneous temperature conversions to	its power-on value. It
       also affects the	resolution value used by latesttemp, to	scale the lat-
       est  conversion value, so make sure to re-sample	the temperature	before
       accessing latesttemp after writing or reading the tempres value.

MEMORY
       Only the	MAX31826 supports memory functions.

   pages/page.0	.. pages/page.15 pages/page.ALL
       read/write, binary
       EEPROM memory pages of 8	bytes each. See	the  datasheet	about  locking
       contents.

   memory
       read/write, binary
       EEPROM memory of	128 bytes. See the datasheet about locking contents.

FAULT REPORTING
       Only the	MAX31850 MAX31851 supports fault reporting.

   fault
       read-only, yes-no
       Fault in	last thermocouple conversion

   open_circuit
       read-only, yes-no
       Thermocouple leads disconnected.

   ground_short
       read-only, yes-no
       Thermocouple lead shorted to ground.

   vdd_short
       read-only, yes-no
       Thermocouple lead shorted to supply voltage.

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	hexadecimal digits (0-9A-F).

   family
       read-only, ascii
       The  8-bit  family  code. Unique	to each	type of	device.	Given as upper
       case hexadecimal	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 hexadecimal 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 hexadecimal)	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.

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 principle 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 fundamental goal has been ease of use,  flexibil-
       ity and correctness rather than speed.

   DS1825
       The  DS1825 (3) is one of several available 1-wire temperature sensors.
       Alternatives are	the DS18S20 (3), DS18B20 (3), and DS1822 (3)  as  well
       as  temperature/voltage	measurements in	the DS2436 (3) and DS2438 (3).
       For truly versatile temperature measurements, see  the  protean	DS1921
       (3) Thermachron (3).

       The   DS1825   (3)   can	  select  between  4  resolutionsspanning  the
       fastest/roughest	and slowest/best.

   MAX31826
       The MAX31826 shares a family code with the DS1825 but  has  differences
       in some of its functions.

       The  MAX31826  has  128	btes of	EEPROM memory (as 16 pages of 8	bytes)
       while the DS1825	has no memory available.

       The MAX31826 measures temperature at 12 bit resolution as fast  as  the
       DS1825's	 lowest	resolution (and	always uses 12-bit resolution).	On the
       other hand it has no temperature	thresholds or alarm function.

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 hexadecimal,	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.

       Both  the  MAX31826  and	the DS1825 allow hardware selection of part of
       the address, which can assist selecting between chips is	 some  circuit
       designs.

DATASHEET
       DS1825 http://pdfserv.maxim-ic.com/en/ds/DS1825.pdf

       MAX31826
	      http://datasheets.maxim-ic.com/en/ds/MAX31826.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 (3) EDS0066 (3) EDS0068 (3)

   Moisture
       EEEF (3)	DS2438 (3)

AVAILABILITY
       http://www.owfs.org

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

OWFS Manpage			     2006			     DS1825(3)

NAME | SYNOPSIS | FAMILY CODE | SPECIAL PROPERTIES | TEMPERATURE ALARM LIMITS | TEMPERATURE RESOLUTION DEFAULT VALUE | MEMORY | FAULT REPORTING | STANDARD PROPERTIES | DESCRIPTION | ADDRESSING | DATASHEET | SEE ALSO | AVAILABILITY | AUTHOR

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