Provided by: owfs-doc_3.1p5-2_all bug

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  |
       latesttemp  | 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.

   latesttemp
       read-only, floating point
       Latest  measured  temperature.  Reading  this  node  will  never  trigger  a   temperature
       conversion. Intended for use in conjunction with /simultaneous/temperature.

   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 hexadecimal 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 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 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  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.

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 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.

       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 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 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.

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) 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) Egil Kvaleberg