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DS2438(3)		     One-Wire File System		     DS2438(3)

NAME
       DS2438 -	Smart Battery Monitor

SYNOPSIS
   Temperature Voltages	and Current.
       26  [.]XXXXXXXXXXXX[XX][/[  CA  | EE | date | disconnect/date | discon-
       nect/udate  |  endcharge/date  |	 endcharge/udate  |  IAD  |  offset  |
       pages/page.[0-7|ALL]  | temperature | udate | VAD | VDD | vis | address
       | crc8 |	id | locator | r_address | r_id	| r_locator | type ]]

   Humidity sensor
       26  [.]XXXXXXXXXXXX[XX][/[  HIH4000/humidity   |	  HTM1735/humidity   |
       DATANAB/reset | DATANAB/humidity	| humidity | temperature ]]

   Barometer
       26    [.]XXXXXXXXXXXX[XX][/[    B1-R1-A/pressure	  |   B1-R1-A/gain   |
       B1-R1-A/offset |	]]

   Light
       26  [.]XXXXXXXXXXXX[XX][/[  S3-R1-A/current  |  S3-R1-A/illuminance   |
       S3-R1-A/gain ]]

FAMILY CODE
       26

SPECIAL	PROPERTIES
   pages/page.0	... pages/page.7 pages/page.ALL
       read-write, binary
       Memory  is  split  into 8 pages of 8 bytes each.	Only the pages 3-7 are
       really available, and some of that appears  to  be  reserved.  See  the
       datasheet for details.
       ALL is an aggregate of the pages. Each page is accessed sequentially.

   temperature
       read-only, floating point
       Temperature  read  by the chip at high resolution (~13 bits). Units are
       selected	from the invoking command line.	See owfs(1) or owhttpd(1)  for
       choices.	Default	is Celsius.  Conversion	takes ~20 msec.

   VAD VDD
       read-only, floating point
       Voltage	read  (~10 bits) at the	one of the chip's two supply voltages.
       Range VDD= 2.4V to 10V, VAD=1.5 to 10V.

   vis
       read-only, floating point
       Current sensor reading, as a voltage difference.	Value is in volts.
       Actual current depends on Rsens resistor	(see datasheet).
       The formula for current is I = vis / Rsens
       with units in Amps and Ohms.
       Current measurement will	be temporarily enabled (see Ienable )  if  not
       currently enabled (pun intended)	for this reading.

CONFIGURATION PROPERTIES
   CA
       read-write, yes-no
       Current	Accumulator  Configuration  flag  bit.	If "on"	(1) current is
       stored in page 7	bytes 4-7. If "off" (0)	that page can be used for gen-
       eral storage. See the datasheet for more	information.

   EE
       read-write, yes-no
       Current	Accumulator  Shadow  flag  bit.	If "on"	(1) current reading is
       stored to EEPROM. If "off" (0) that data	will be	lost when  chip	 loses
       power. See the datasheet	for more information

   IAD
       read-write, yes-no
       Current A/D Control flag	bit. If	"on" (1) current measured at 36.41 Hz.
       If "off"	(0) current measurements won't be made.	See the	datasheet  for
       more information.

DATE PROPERTIES
   date
       read-write, ascii
       26  character date representation of the	counter	value. Increments once
       per second.
       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)

   disconnect/date
       read-write, ascii
       26 character date representation	of the	disconnect/udate  value.  Time
       when the	battery	pack waws removed from the charger. Format is the same
       as the date property.

   disconnect/udate
       read-write, unsigned integer
       Representation of disconnect/date as a number. See udate	for details.

   endcharge/date
       read-write, ascii
       26 character date representation	of the endcharge/udate	value.	Format
       is the same as the date property.

   endcharge/udate
       read-write, unsigned integer
       Representation of endcharge/date	as a number. See udate for details.

   udate
       read-write, unsigned integer
       Time represented	as a number.  udate increments once per	second.
       Usually set to unix time	standard: number of seconds since Jan 1, 1970.
       The date	field will be the unix representation (ascii  text)  of	 udate
       and setting either will change the other.

HUMIDITY PROPERTIES
   HIH4000/humidity
       read-only, floating point
       Relative	humidity, as percent (1-100 scale).
       This  value is for a design based on Honeywell's	HIH-4000 humidity sen-
       sor.

   HTM1735/humidity
       read-only, floating point
       Relative	humidity, as percent (1-100 scale).
       This value is for a design based	on Humirel's HTM-1735 humidity sensor.

   DATANAB/humidity
       read-only, floating point
       Based on	DataNAB's humidity sensor. It uses a HIH-4000 sensor  and  the
       current sensning	rather than voltage readings from the DS2438. Calibra-
       tion values are stored on chip, and a check field  is  stored  in  chip
       memory.

   DATANAB/reset
       write-only, yes-no
       Used  to	 read  calibration  values and set the chip to current reading
       more. Should be automatically called when a  humidity  reading  is  re-
       quested.

   humidity
       read-only, floating point
       Relative	humidity, as percent (1-100 scale).
       The  DS2438 actually does not read humidity, but	a widely available and
       publicised circuit based	on the chip, does. This	design is for the com-
       mon  Honeywell  HIH-3610	 humidity chip.	The mostly compatible HIH-4000
       chip uses different temperature compensation, so	is  better  read  from
       the HIH4000/humidity value. See the datasheets for details.
       If  the	chip  is  instead a DATANAB design, the	DATANAB/humidity value
       will be automatically used.

BAROMETER PROPERTIES
   B1-R1-A/pressure
       read-only, floating point
       Pressure	reading, as  milli-bars,  or  other  unit  depending  on  set-
       tings/units/pressure_scale.
       This  value is for the B1-R1-A barometer	from Hobby-Boards, and assumes
       the standard calibration.

   B1-R1-A/gain
       read/write, floating point
       Calibration of pressure gain, as	signed number, expressed as  the  same
       units as	B1-R1-A/pressure per volt.
       This  value  will  be  multiplied  with the measured voltage to get the
       B1-R1-A/pressure	reading. It may	have to	be fine	tuned for  calibration
       purposes,  although  with  the  standard	 sensor, it will often be good
       enough to keep it as is.

   B1-R1-A/offset
       read/write, floating point
       Calibration of  pressure	 offset,  as  signed  number,  same  units  as
       B1-R1-A/pressure.
       This  value  will be added to the B1-R1-A/pressure reading. The default
       value is	904.7 millibars, which may be altered to to compensate for el-
       evation.

SOLAR SENSOR PROPERTIES
   S3-R1-A/current
       read-only, floating point
       Photo-diode current, in micro-amperes.
       This value is for the S3-R1-A solar radiation sensor from Hobby-Boards.
       Due to noise and	offsets, this value may	read as	a negative  number  in
       low  light  conditions.	 The offset register can be modified to	reduce
       the offset as much as possible.

   S3-R1-A/illumination
       read-only, floating point
       Illumination, in	lux. Always a positive number.
       This  value  is	the  lux  reading  from	 the  solar   sensor,	taking
       S3-R1-A/gain into consideration.

   S3-R1-A/gain
       read/write, floating point
       Calibration  of	photo-diode  gain  expressed as	lux per	micro-amperes.
       The default value is for	the SFH203P photo-diode	from Osram, used bare.
       A  different  gain  may be used for instance to compensate for an inte-
       grathing, white sphere placed over the diode.
       This value is for the S3-R1-A solar radiation sensor from Hobby-Boards,
       using the SFH203P photo-diode from Osram.

MULTISENSOR PROPERTIES
   MultiSensor/type
       read-only, ascii
       For iButtonLink's MultiSensor line of 1-wire devices, give the specific
       configuration based on a	data byte set in memory. (Byte 0 of  page  3).
       This can	help interpretation of the sensor values, distinguishing, cur-
       rent from water from light.

   offset
       read-write, integer
       Correction for current readings.	A value	between	-256 and 255. See  the
       datasheet  for  details.	 Should	 be set	to the negative	of a true zero
       current reading.

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.

   DS2438
       The DS2438 (3) is a more	complete form of the DS2436 battery chip. Cur-
       rent  sensing  is  available,  but not implemented. The major advantage
       compared	to the DS2436 is that two voltages can be read,	 allowing  one
       to  correct  circuit measurements for supply voltage and	temperature. A
       better comparison is the	DS276x family of chips.

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
       http://goo.gl/o9DH0  (Redirects	to  009012_2.pdf  PDF  file  on	honey-
       well.com	website)
       http://www.phanderson.com/hih-4000.pdf
       http://www.humirel.com/product/fichier/HTM1735%20RevG%20.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) Egil Kvaleberg

OWFS Manpage			     2003			     DS2438(3)

NAME | SYNOPSIS | FAMILY CODE | SPECIAL PROPERTIES | CONFIGURATION PROPERTIES | DATE PROPERTIES | HUMIDITY PROPERTIES | BAROMETER PROPERTIES | SOLAR SENSOR PROPERTIES | MULTISENSOR PROPERTIES | STANDARD PROPERTIES | ALARMS | DESCRIPTION | ADDRESSING | DATASHEET | SEE ALSO | AVAILABILITY | AUTHOR

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