DS2770(3)

NAME

DS2770
    Battery Monitor and Charge Controller

SYNOPSIS

  Temperature Voltage Current Memory and Switch.

2E [.]XXXXXXXXXXXX[XX][/[ amphours | current | currentbias | lock.[0-2|ALL] | memory | pages/page.[0-2|ALL] | PIO | sensed | temperature | vbias | vis | volt | volthours |
charge | cini | cstat0 | cstat1 | ctype | defaultpmod | pmod | refresh | timer |
]]

  Thermocouple

2E [.]XXXXXXXXXXXX[XX][/[ temperature | typeX/range_low | typeX/range_high | typeX/temperature

FAMILY CODE

2E

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.[0-2|ALL]
read-write, yes-no
Lock either of the three 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.[0-2|ALL]
read-write, binary Two 16 byte and one 8 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.

  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

THERMOCOUPLE

  typeX/
directory
Thermocouple circuit using the DS2770 (3) 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.

OBSCURE PROPERTIES

  charge
write-only, yes-no
Trigger the start (1) or stop(0) of charging. see the DATASHEET for details.

  cini cstat0 cstat1 ctype pmod
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
read-write, yes-no
Default power-on state for the corresponding properties.

  refresh
write-only, yes-no
Writing anything to this file causes a refresh of parameters. See the

  timer
read-write, floating point
A charge timer in units of hours. See the DATASHEET for details.

STANDARD PROPERTIES

ALARMS
None.

DESCRIPTION

  DS2770
The DS2770 (3) is a battery charging controller. It has elaborate charge estimation algorithms built in.

A number of interesting devices can be built with the DS2770 including thermocouples. Support for thermocouples in built into the software, using the embedded thermister as the cold junction temperature.

ADDRESSING

DATASHEET
http://pdfserv.maxim-ic.com/en/ds/DS2770.pdf

SEE ALSO

AVAILABILITY
http://www.owfs.org

AUTHOR
Paul Alfille (paul.alfille@gmail.com)