DS2751 - Multichemistry Battery Fuel Gauge

Addressing

       All 1-wire devices are factory assigned a unique 64-bit address. This address is of the form:

       FamilyCode
              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.

Alarms

       None.

Author

       Paul Alfille (paul.alfille@gmail.com)

OWFS Manpage                                          2003                                             DS2751(3)

Availability

http://www.owfs.org

Datasheet

http://pdfserv.maxim-ic.com/en/ds/DS2751.pdf

Description

1-Wire1-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 busmaster 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.

OWFSdesignOWFS 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 fundamental goal has been ease of use,
flexibility and correctness rather than speed.

DS2751
The DS2751(3) is battery charging controllers similar to the DS2760(3)

A number of interesting devices can be built with the DS2751(3) including thermocouples. Support for
thermocouples in built into the software, using the embedded thermister as the cold junction temperature.

Family Code

Name

DS2751 - Multichemistry Battery Fuel Gauge

Obscure Properties

pmodporuvenvaries,yes-no
       Bit  flags  corresponding  to  various  battery  management  functions of the chip. See the DATASHEET for
       details of the identically named entries.
       In general, writing "0" corresponds to a 0 bit value, and non-zero corresponds to a 1 bit value.

   defaultpmodread-write,yes-no
       Default power-on state for the corresponding properties.

Special Properties

amphoursread-write,floatingpoint
Accumulated amperage read by current sensor. Units are in Amp-hr (Assumes internal 25mOhm resistor).
Derived from volthours / Rinternal.
Formally amphours is the integral of current-currentbias over time.

currentread-only,floatingpoint
Current reading. Units are in Amp (Assumes internal 25 mOhm resistor). Derived from vis / Rinternal.

currentbiasread-write,floatingpoint
Fixed offset applied to each current measurement. Used in the amphours value. Assumes internal 25mOhm
resistor. Units are Amp and range from -.08A to .08A.
Derived from vbias / Rinternal.

lock.[0-1|ALL]read-write,yes-no
Lock either of the two eprom pages to prevent further writes. Apparently setting lock is permanent.

memoryread-write,binary
Access to the full 256 byte memory range. Much of this space is reserved or special use. User space is
the page area.
See the DATASHEET for a full memory map.

pages/pages.[0-1|ALL]read-write,binary Two 16 byte areas of memory for user application. The lock property can prevent
further alteration.
NOTE that the page property is different from the common OWFS implementation in that all of memory is not
accessible.

PIOwrite-only,yes-no
Controls the PIO pin allowing external switching.
Writing "1" turns the PIO pin on (conducting). Writing "0" makes the pin non-conducting. The logical
state of the voltage can be read with the sensed property. This will reflect the current voltage at the
pin, not the value sent to PIO
Note also that PIO will also be altered by the power-status of the DS2670 See the datasheet for details.

sensedread-only,yes-no
The logical voltage at the PIO pin. Useful only if the PIO property is set to "0" (non-conducting).
Value will be 0 or 1 depending on the voltage threshold.

temperatureread-only,floatingpointTemperature 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 is continuous.

vbiasread-write,floatingpoint
Fixed offset applied to each vis measurement. Used for the volthours value. Units are in Volts.
Range -2.0mV to 2.0mV

visread-only,floatingpoint
Current sensor reading (unknown external resistor). Measures the voltage gradient between the Vis pins.
Units are in Volts
The vis readings are integrated over time to provide the volthours property.
The current reading is derived from vis assuming the internal 25 mOhm resistor is employed. There is no
way to know this through software.

voltread-only,floatingpoint
Voltage read at the voltage sensor;. This is separate from the vis voltage that is used for current
measurement. Units are Volts
Range is between 0 and 4.75V

volthoursread-write,floatingpoint
Integral of vis-vbias over time. Units are in volthours

Standard Properties

addressr_addressread-only,ascii
The entire 64-bit unique ID. Given as upper case hexadecimal digits (0-9A-F).
address starts with the family code
raddress is the address in reverse order, which is often used in other applications and labeling.

crc8read-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).

familyread-only,ascii
The 8-bit family code. Unique to each type of device. Given as upper case hexadecimal digits (0-9A-F).

idr_idread-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).
rid is the id in reverse order, which is often used in other applications and labeling.

locatorr_locatorread-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 LinkLocator the locatorwillshowaunique8-bytenumber(16characterhexadecimal)startingwithfamilycodeFE.
If no LinkLocator is between the device and the master, the locator field will be all FF.
rlocator is the locator in reverse order.

present(DEPRECATED)read-only,yes-no
Is the device currently present on the 1-wire bus?

typeread-only,ascii
Part name assigned by Dallas Semi. E.g. DS2401 Alternative packaging (iButton vs chip) will not be
distiguished.

Synopsis

TemperatureVoltage,Current,Memory,andSwitch.51   [.]XXXXXXXXXXXX[XX][/[   amphours   |   current   |   currentbias   |   lock.[0-1|ALL]  |  memory  |
       pages/page.[0-1|ALL]  |  PIO  |  sensed  |   temperature   |   typeX/range_low   |   typeX/range_high   |
       typeX/temperature | vbias | vis | volt | volthours |
       defaultpmod | pmod | por | uven |
       address | crc8 | id | locator | r_address | r_id | r_locator | type ]]

   Thermocouple51 [.]XXXXXXXXXXXX[XX][/[ temperature | typeX/range_low | typeX/range_high | typeX/temperature

Thermocouple

typeX/directory
       Thermocouple  circuit  using  the DS2760 to read the Seebeck voltage and the reference temperature. Since
       the type interpretation of the values read depends on the type of  thermocouple,  the  correct  directory
       must be chosen. Supported thermocouple types include types B, E, J, K, N, R, S and T.

   typeX/range_lowtypeX/ranges_highread-only,flaotingpoint
       The  lower and upper temperature supported by this thermocouple (at least by the conversion routines). In
       the globally chosen temperature units.

   typeX/temperatureread-only,floatingpoint
       Thermocouple temperature. Requires a voltage and temperature  conversion.  Returned  in  globally  chosen
       temperature units.
       Note:  there are two types of temperature measurements possible. The temperature value in the main device
       directory is the reference  temperature  read  at  the  chip.  The  typeX/temperature  value  is  at  the
       thermocouple junction, probably remote from the chip.

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