Ubuntu Manpage: DS2438 - Smart Battery Monitor

Provided by: owfs-doc_2.8p15-1ubuntu4_all

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

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

AVAILABILITY

       http://www.owfs.org

AUTHOR

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