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NAME

       DS2438 - Smart Battery Monitor

SYNOPSIS

   Temperature Voltages and Current.
       26  [.]XXXXXXXXXXXX[XX][/[  CA  |  EE  |  date  |  disconnect/date  |  disconnect/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 general 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 sensor.

   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. Calibration 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 requested.

   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 common 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 settings/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 elevation.

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 integrathing, 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, current 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. Computed from the
       preceding 56 bits of the unique ID number. Given as upper 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 applications 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 manufactured 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 (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.

       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, parallel, 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 individual 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
       communication.  Still  the  fundemental  goal  has  been  ease  of  use,  flexibility  and
       correctness rather than speed.

   DS2438
       The DS2438 (3) is a more complete form of the DS2436  battery  chip.  Current  sensing  is
       available,  but  not  implemented.  The major advantage compared to the DS2436 is that two
       voltages can be read, allowing correcting circuit  nmeasurements  to  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 honeywell.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)

   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)

AVAILABILITY

       http://www.owfs.org

AUTHOR

       Paul Alfille (paul.alfille@gmail.com) Egil Kvaleberg