Ubuntu Manpage: DS2437 - Smart Battery Monitor

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

NAME

       DS2437 - Smart Battery Monitor

SYNOPSIS

       Temperature Voltages and Memory.

       1E   [.]XXXXXXXXXXXX[XX][/[   current  |  date  |  disconnect/date  |  disconnect/udate  |
       endcharge/date | endcharge/udate | Ienable | pages/page.[0-7|ALL] | temperature | udate  |
       VAD | VDD | address | crc8 | id | locator | r_address | r_id | r_locator | type ]]

FAMILY CODE

1E

SPECIAL 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)

current
read-only, integer
Current reading. Actual current depends on Rsens resistor (see datasheet).
The formula for current is I = current /(4096*Rsens)
with units in Amps and Ohms.
Current measurement will be temporarily enabled (see Ienable ) if not currently enabled
(pun intended) for this reading.

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.

Ienable
read-write, unsigned integer
Status of current monitoring. When enabled, current sensing is performed 36.41
times/second. Values of Ienable are:

0 no current conversion

1 current conversion enabled

2 current conversion and accumulation

3 current conversion and accumulation with EEPROM backup

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.

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.

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.

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.

DS2437
The DS2437 (3) is an obsolete version of the DS2438 (3) 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/DS2437.pdf
       http://pdfserv.maxim-ic.com/en/an/humsensor.pdf

AVAILABILITY

       http://www.owfs.org

AUTHOR

       Paul Alfille (paul.alfille@gmail.com)