DS2770(3)

1DS2770(3)                    One-Wire File System                    DS2770(3)
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NAME

6       DS2770 - Battery Monitor and Charge Controller
7

SYNOPSIS

9   Temperature Voltage Current Memory and Switch.
10       2E   [.]XXXXXXXXXXXX[XX][/[   amphours   |   current  |  currentbias  |
11       lock.[0-2|ALL] | memory | pages/page.[0-2|ALL] | PIO | sensed | temper‐
12       ature | vbias | vis | volt | volthours |
13       charge  | cini | cstat0 | cstat1 | ctype | defaultpmod | pmod | refresh
14       | timer |
15       address | crc8 | id | locator | r_address | r_id | r_locator | type ]]
16
17   Thermocouple
18       2E   [.]XXXXXXXXXXXX[XX][/[    temperature    |    typeX/range_low    |
19       typeX/range_high | typeX/temperature
20

FAMILY CODE

22       2E
23

SPECIAL PROPERTIES

25   amphours
26       read-write, floating point
27       Accumulated  amperage  read  by  current  sensor.  Units  are in Amp-hr
28       (Assumes internal 25mOhm resistor). Derived from volthours / Rinternal.
29       Formally amphours is the integral of current - currentbias over time.
30
31   current
32       read-only, floating point
33       Current reading. Units are in Amp (Assumes internal 25 mOhm  resistor).
34       Derived from vis / Rinternal.
35
36   currentbias
37       read-write, floating point
38       Fixed  offset applied to each current measurement. Used in the amphours
39       value. Assumes internal 25mOhm resistor. Units are Amp and  range  from
40       -.08A to .08A.
41       Derived from vbias / Rinternal.
42
43   lock.[0-2|ALL]
44       read-write, yes-no
45       Lock  either of the three eprom pages to prevent further writes. Appar‐
46       ently setting lock is permanent.
47
48   memory
49       read-write, binary
50       Access to the full 256  byte  memory  range.  Much  of  this  space  is
51       reserved or special use. User space is the page area.
52       See the DATASHEET for a full memory map.
53
54   pages/pages.[0-2|ALL]
55       read-write, binary Two 16 byte  and one 8 byte areas of memory for user
56       application. The lock property can prevent further alteration.
57       NOTE that the page property is different from the common OWFS implemen‐
58       tation in that all of memory is not accessible.
59
60   PIO
61       write-only, yes-no
62       Controls the PIO pin allowing external switching.
63       Writing  "1"  turns  the PIO pin on (conducting). Writing "0" makes the
64       pin non-conducting.  The logical state of the voltage can be read  with
65       the  sensed property. This will reflect the current voltage at the pin,
66       not the value sent to PIO
67       Note also that PIO will also be altered  by  the  power-status  of  the
68       DS2670 See the datasheet for details.
69
70   sensed
71       read-only, yes-no
72       The  logical voltage at the PIO pin. Useful only if the PIO property is
73       set to "0" (non-conducting).
74       Value will be 0 or 1 depending on the voltage threshold.
75
76   temperature
77       read-only, floating point
78       Temperature read by the chip at high resolution (~13 bits).  Units  are
79       selected  from the invoking command line. See owfs(1) or owhttpd(1) for
80       choices. Default is Celsius.
81       Conversion is continuous.
82
83   vbias
84       read-write, floating point
85       Fixed offset applied to each vis measurement. Used  for  the  volthours
86       value. Units are in Volts.
87       Range -2.0mV to 2.0mV
88
89   vis
90       read-only, floating point
91       Current  sensor reading (unknown external resistor). Measures the volt‐
92       age gradient between the Vis pins. Units are in Volts
93       The vis readings are integrated over  time  to  provide  the  volthours
94       property.
95       The  current  reading is derived from vis assuming the internal 25 mOhm
96       resistor is employed. There is no way to know this through software.
97
98   volt
99       read-only, floating point
100       Voltage read at the voltage sensor;. This  is  separate  from  the  vis
101       voltage that is used for current measurement. Units are Volts
102       Range is between 0 and 4.75V
103
104   volthours
105       read-write, floating point
106       Integral of vis - vbias over time. Units are in volthours
107

THERMOCOUPLE

109   typeX/
110       directory
111       Thermocouple  circuit  using the DS2770 (3) to read the Seebeck voltage
112       and the reference temperature. Since the  type  interpretation  of  the
113       values  read depends on the type of thermocouple, the correct directory
114       must be chosen. Supported thermocouple types include types B, E, J,  K,
115       N, R, S and T.
116
117   typeX/range_low typeX/ranges_high
118       read-only, flaoting point
119       The  lower  and  upper  temperature  supported by this thermocouple (at
120       least by the conversion routines). In the globally  chosen  temperature
121       units.
122
123   typeX/temperature
124       read-only, floating point
125       Thermocouple  temperature.  Requires  a voltage and temperature conver‐
126       sion. Returned in globally chosen temperature units.
127       Note: there are two types of  temperature  measurements  possible.  The
128       temperature value in the main device directory is the reference temper‐
129       ature read at the chip. The typeX/temperature value is at  the  thermo‐
130       couple junction, probably remote from the chip.
131

OBSCURE PROPERTIES

133   charge
134       write-only, yes-no
135       Trigger  the  start  (1)  or stop(0) of charging. see the DATASHEET for
136       details.
137
138   cini cstat0 cstat1 ctype pmod
139       varies, yes-no
140       Bit flags corresponding to various battery management functions of  the
141       chip. See the DATASHEET for details of the identically named entries.
142       In general, writing "0" corresponds to a 0 bit value, and non-zero cor‐
143       responds to a 1 bit value.
144
145   defaultpmod
146       read-write, yes-no
147       Default power-on state for the corresponding properties.
148
149   refresh
150       write-only, yes-no
151       Writing anything to this file causes a refresh of parameters. See the
152
153   timer
154       read-write, floating point
155       A charge timer in units of hours.  See the DATASHEET for details.
156

STANDARD PROPERTIES

158   address
159   r_address
160       read-only, ascii
161       The entire 64-bit unique ID. Given as  upper  case  hexidecimal  digits
162       (0-9A-F).
163       address starts with the family code
164       r address is the address in reverse order, which is often used in other
165       applications and labeling.
166
167   crc8
168       read-only, ascii
169       The 8-bit error correction portion. Uses cyclic redundancy check.  Com‐
170       puted  from  the  preceding  56  bits of the unique ID number. Given as
171       upper case hexidecimal digits (0-9A-F).
172
173   family
174       read-only, ascii
175       The 8-bit family code. Unique to each type of device.  Given  as  upper
176       case hexidecimal digits (0-9A-F).
177
178   id
179   r_id
180       read-only, ascii
181       The 48-bit middle portion of the unique ID number. Does not include the
182       family code or CRC. Given as upper case hexidecimal digits (0-9A-F).
183       r id is the id in reverse order, which is often used in other  applica‐
184       tions and labeling.
185
186   locator
187   r_locator
188       read-only, ascii
189       Uses  an  extension  of the 1-wire design from iButtonLink company that
190       associated 1-wire physical connections with a unique  1-wire  code.  If
191       the  connection is behind a Link Locator the locator will show a unique
192       8-byte number (16 character hexidecimal) starting with family code FE.
193       If no Link Locator is between the device and the  master,  the  locator
194       field will be all FF.
195       r locator is the locator in reverse order.
196
197   present (DEPRECATED)
198       read-only, yes-no
199       Is the device currently present on the 1-wire bus?
200
201   type
202       read-only, ascii
203       Part  name  assigned by Dallas Semi. E.g.  DS2401 Alternative packaging
204       (iButton vs chip) will not be distiguished.
205

ALARMS

207       None.
208

DESCRIPTION

210   1-Wire
211       1-wire is a wiring protocol and series of devices designed and manufac‐
212       tured  by  Dallas  Semiconductor, Inc. The bus is a low-power low-speed
213       low-connector scheme where the data line can also provide power.
214
215       Each device is uniquely and unalterably  numbered  during  manufacture.
216       There  are a wide variety of devices, including memory, sensors (humid‐
217       ity, temperature, voltage, contact, current), switches, timers and data
218       loggers.  More complex devices (like thermocouple sensors) can be built
219       with these basic devices. There  are  also  1-wire  devices  that  have
220       encryption included.
221
222       The  1-wire  scheme uses a single bus master and multiple slaves on the
223       same wire. The bus master initiates all communication. The  slaves  can
224       be individually discovered and addressed using their unique ID.
225
226       Bus  masters come in a variety of configurations including serial, par‐
227       allel, i2c, network or USB adapters.
228
229   OWFS design
230       OWFS is a suite of programs that designed to make the  1-wire  bus  and
231       its  devices easily accessible. The underlying principle is to create a
232       virtual filesystem, with the unique ID being  the  directory,  and  the
233       individual  properties  of  the  device are represented as simple files
234       that can be read and written.
235
236       Details of the individual slave or master design are  hidden  behind  a
237       consistent interface. The goal is to provide an easy set of tools for a
238       software designer to create monitoring or control  applications.  There
239       are some performance enhancements in the implementation, including data
240       caching, parallel access to bus masters, and aggregation of device com‐
241       munication.  Still the fundemental goal has been ease of use, flexibil‐
242       ity and correctness rather than speed.
243
244   DS2770
245       The DS2770 (3) is a  battery  charging  controller.  It  has  elaborate
246       charge estimation algorithms built in.
247
248       A  number of interesting devices can be built with the DS2770 including
249       thermocouples. Support for thermocouples in built  into  the  software,
250       using the embedded thermister as the cold junction temperature.
251

ADDRESSING

253       All  1-wire  devices are factory assigned a unique 64-bit address. This
254       address is of the form:
255
256       Family Code
257              8 bits
258
259       Address
260              48 bits
261
262       CRC    8 bits
263
264       Addressing under OWFS is in hexidecimal, of form:
265
266              01.123456789ABC
267
268       where 01 is an example 8-bit family code, and 12345678ABC is an example
269       48 bit address.
270
271       The  dot  is  optional,  and the CRC code can included. If included, it
272       must be correct.
273

DATASHEET

275       http://pdfserv.maxim-ic.com/en/ds/DS2770.pdf
276

AVAILABILITY

338       http://www.owfs.org
339

AUTHOR

341       Paul Alfille (paul.alfille@gmail.com)
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345OWFS Manpage                         2003                            DS2770(3)