DS2755(3)

NAME
DS2755 DS2756 - Multichemistry Battery Fuel Gauge

SYNOPSIS
Temperature Voltage, Current, Memory, and Switch.

35 [.]XXXXXXXXXXXX[XX][/[ alarm_set/[volthigh|voltlow|temphigh|templow] | lock.[0-2|ALL] | memory | pages/page.[0-2|ALL] | PIO | sensed | temperature | typeX/range_low | typeX/range_high | typeX/temperature | vbias | vis | volt | volthours |
defaultpmod | pie0 | pie1 | rnaop | ios | uben | ovd | pmod | por | uven |
]]

FAMILY CODE

35

SPECIAL PROPERTIES

  alarm_set/templow alarm_set/temphigh
read-write, integer
High and low alarm settings for temperature

  alarm_set/voltlow alarm_set/volthigh
read-write, floating point
High and low alarm settings for volts

  lock.[0-2|ALL]
read-write, yes-no
Lock any 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 Three 32 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 DS2755 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

  pmod por uven pie0 pie1 ios uben ovd rnaop
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.

STANDARD PROPERTIES

ALARMS
Temperature and voltage.

DESCRIPTION

  DS2755 DS2756
The DS2755 (3) and DS2756 (3) are battery charging controllers similar to the DS2751 (3) except no internal resistor option and a larger EEPROM memory.

The DS2756 (3) adds suspend modes ( pie0 pie1 ) to the DS2755 (3)

A number of interesting devices can be built with the DS2755 (3) and DS2756 (3) 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/DS2755.pdf
http://pdfserv.maxim-ic.com/en/ds/DS2756.pdf

SEE ALSO

AVAILABILITY
http://www.owfs.org

AUTHOR
Paul Alfille (palfille@earthlink.net)