DS2770(3) One-Wire File System DS2770(3)NAMEDS2770 - 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 | temper‐
ature | 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. Appar‐
ently 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 implemen‐
tation 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 volt‐
age 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 conver‐
sion. 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 temper‐
ature read at the chip. The typeX/temperature value is at the thermo‐
couple 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 cor‐
responds 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 PROPERTIESALARMS
None.
DESCRIPTIONDS2770
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.
ADDRESSINGDATASHEET
http://pdfserv.maxim-ic.com/en/ds/DS2770.pdf
SEE ALSOAVAILABILITY
http://www.owfs.org
AUTHOR
Paul Alfille (paul.alfille@gmail.com)
OWFS Manpage 2003 DS2770(3)
