Ubuntu Manpage: DS2437 - Smart Battery Monitor

name
synopsis
family code
special properties
standard properties
alarms
description
addressing
datasheet
see also
availability
author

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 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.

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 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/DS2437.pdf
       http://pdfserv.maxim-ic.com/en/an/humsensor.pdf

AVAILABILITY

       http://www.owfs.org

AUTHOR

       Paul Alfille (paul.alfille@gmail.com)