Ubuntu Manpage: DS2438 - Smart Battery Monitor

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

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

AVAILABILITY

       http://www.owfs.org

AUTHOR

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