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Table of Contents

Name

DS2760 DS2761 DS2762 - High-Precision Li+ Battery Monitor

Synopsis

Temperature Voltage and Current.

30 [.]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 |
cc | ce | coc | defaultpmod | defaultswen | dc | de | doc | mstr | ov | ps | pmod | swen | uv |
address | crc8 | id | locator | present | r_address | r_id | r_locator | type ]]

Family Code

30

Special Properties

amphours

read-write, floating point
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.

current

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

currentbias

read-write, floating point
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.

memory

read-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.

Pio

write-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.

sensed

read-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.

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 is continuous.

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_low typeX/ranges_high

read-only, flaoting point
The lower and upper temperature supported by this thermocouple (at least by the conversion routines). In the globally chosen temperature units.

typeX/temperature

read-only, floating point
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.

vbias

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

vis

read-only, floating point
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.

volt

read-only, floating point
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

volthours

read-write, floating point
Integral of vis - vbias over time. Units are in volthours

Obscure Properties

cc ce coc dc de doc mstr ov pmod swen uv

varies, 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.

defaultpmod defaultswen

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

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 preceeding 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

read-only, yes-no
Is the device currently present on the 1-wire bus?
Note, this means that each hex byte (2 characters) is reversed, not the text string.

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 Semicondictor, Inc. The bus is a low-power low-speed low-connector scheme where the data line can also provide power.

Each device is uniquely unalterably numbered during manufacture. There is a wide variety of devices, including memory, sensors (humidity, temperature, voltage, contact, current), switches, timers, loggers, and more complex devices (like thermocouple sensors) can be built wit hte basic devices. There are also 1-wire devices that have encryption included.

The 1-wire bus is accessed via one of a number of serial, parallel or USB adapters.

OWFS design

OWFS is a suite of programs that fundementally 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 files.

There is optional data caching to improved performance, but possible confusion over stale data.

Ds2760 Ds2761 Ds2762

The DS2760 (3) is a class of battery charging controllers. There are minor hardware difference between the DS2760, DS2761 and DS2762 battery chip, but they are indistiguishable to the software.

A number of interesting devices can be built with the DS276x including thermocouples. Support for thermocouples in built into the software, using the embedded thermister as the cold junction temperature.

For an explanatino of the differences between the DS276x variants, see Dallas Application Note 221.

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/DS2760.pdf
http://pdfserv.maxim-ic.com/en/an/app221.pdf

See Also

Programs

owfs (1) owhttpd (1) owftpd (1) owserver (1)

Language bindings

owtcl (3) owperl (3)

Clocks

DS1427 (3) DS1904(3) DS1994 (3) DS2404 (3) DS2404S (3) DS2415 (3) DS2417 (3)

ID

DS2401 (3) DS1990A (3)

Memory

DS1982 (3) DS1985 (3) DS1986 (3) DS1991 (3) DS1992 (3) DS1993 (3) DS1995 (3) DS1996 (3) DS2431 (3) DS2433 (3) DS2502 (3) DS2506 (3) DS2804 (3)

Switches

DS2405 (3) DS2406 (3) DS2408 (3) DS2409 (3) DS2413 (3)

Temperature

DS1822 (3) DS18B20 (3) DS18S20 (3) DS1920 (3) DS1921 (3) DS1821 (3)

Humidity

DS1922 (3)

Voltage

DS2450 (3)

Resistance

DS2890 (3)

Multifunction

DS2436 (3) DS2438 (3) DS2760 (3)

Counter

DS2423 (3)

LCD Screen

LCD (3) DS2408 (3)

Crypto

DS1977 (3)

Availability

http://owfs.sourceforge.net

Author

Paul Alfille (palfille@earthlink.net)


Table of Contents

© 2003-4 Paul H. Alfille and The owfs Team
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