DS2751(3)

1DS2751(3)                    One-Wire File System                    DS2751(3)
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NAME

6       DS2751 - Multichemistry Battery Fuel Gauge
7

SYNOPSIS

9   Temperature Voltage, Current, Memory, and Switch.
10       51   [.]XXXXXXXXXXXX[XX][/[   amphours   |   current  |  currentbias  |
11       lock.[0-1|ALL] | memory | pages/page.[0-1|ALL] | PIO | sensed | temper‐
12       ature  | typeX/range_low | typeX/range_high | typeX/temperature | vbias
13       | vis | volt | volthours |
14       defaultpmod | pmod | por | uven |
15       address | crc8 | id | locator | r_address | r_id | r_locator | type ]]
16
17   Thermocouple
18       51   [.]XXXXXXXXXXXX[XX][/[    temperature    |    typeX/range_low    |
19       typeX/range_high | typeX/temperature
20

FAMILY CODE

22       51
23

SPECIAL PROPERTIES

25   amphours
26       read-write, floating point
27       Accumulated  amperage  read by current sensor. Units are in Amp-hr (As‐
28       sumes 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.[0-1|ALL]
44       read-write, yes-no
45       Lock  either  of  the two 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  re‐
51       served or special use. User space is the page area.
52       See the DATASHEET for a full memory map.
53
54   pages/pages.[0-1|ALL]
55       read-write,  binary  Two  16 byte areas of memory for user application.
56       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 DS2760 to read the Seebeck voltage and
112       the reference temperature. Since the type interpretation of the  values
113       read depends on the type of thermocouple, the correct directory must be
114       chosen. Supported thermocouple types include types B, E, J, K, N, R,  S
115       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   pmod por uven
134       varies, yes-no
135       Bit  flags corresponding to various battery management functions of the
136       chip. See the DATASHEET for details of the identically named entries.
137       In general, writing "0" corresponds to a 0 bit value, and non-zero cor‐
138       responds to a 1 bit value.
139
140   defaultpmod
141       read-write, yes-no
142       Default power-on state for the corresponding properties.
143

STANDARD PROPERTIES

145   address
146   r_address
147       read-only, ascii
148       The  entire  64-bit  unique  ID. Given as upper case hexadecimal digits
149       (0-9A-F).
150       address starts with the family code
151       r address is the address in reverse order, which is often used in other
152       applications and labeling.
153
154   crc8
155       read-only, ascii
156       The  8-bit error correction portion. Uses cyclic redundancy check. Com‐
157       puted from the preceding 56 bits of the unique ID number. Given as  up‐
158       per case hexadecimal digits (0-9A-F).
159
160   family
161       read-only, ascii
162       The  8-bit  family  code. Unique to each type of device. Given as upper
163       case hexadecimal digits (0-9A-F).
164
165   id
166   r_id
167       read-only, ascii
168       The 48-bit middle portion of the unique ID number. Does not include the
169       family code or CRC. Given as upper case hexadecimal digits (0-9A-F).
170       r  id is the id in reverse order, which is often used in other applica‐
171       tions and labeling.
172
173   locator
174   r_locator
175       read-only, ascii
176       Uses an extension of the 1-wire design from  iButtonLink  company  that
177       associated  1-wire  physical  connections with a unique 1-wire code. If
178       the connection is behind a Link Locator the locator will show a  unique
179       8-byte number (16 character hexadecimal) starting with family code FE.
180       If  no  Link  Locator is between the device and the master, the locator
181       field will be all FF.
182       r locator is the locator in reverse order.
183
184   present (DEPRECATED)
185       read-only, yes-no
186       Is the device currently present on the 1-wire bus?
187
188   type
189       read-only, ascii
190       Part name assigned by Dallas Semi. E.g.  DS2401  Alternative  packaging
191       (iButton vs chip) will not be distiguished.
192

ALARMS

194       None.
195

DESCRIPTION

197   1-Wire
198       1-wire is a wiring protocol and series of devices designed and manufac‐
199       tured by Dallas Semiconductor, Inc. The bus is  a  low-power  low-speed
200       low-connector scheme where the data line can also provide power.
201
202       Each  device  is  uniquely and unalterably numbered during manufacture.
203       There are a wide variety of devices, including memory, sensors  (humid‐
204       ity, temperature, voltage, contact, current), switches, timers and data
205       loggers. More complex devices (like thermocouple sensors) can be  built
206       with  these  basic devices. There are also 1-wire devices that have en‐
207       cryption included.
208
209       The 1-wire scheme uses a single bus master and multiple slaves  on  the
210       same  wire.  The bus master initiates all communication. The slaves can
211       be individually discovered and addressed using their unique ID.
212
213       Bus masters come in a variety of configurations including serial,  par‐
214       allel, i2c, network or USB adapters.
215
216   OWFS design
217       OWFS  is  a  suite of programs that designed to make the 1-wire bus and
218       its devices easily accessible. The underlying principle is to create  a
219       virtual filesystem, with the unique ID being the directory, and the in‐
220       dividual properties of the device are represented as simple files  that
221       can be read and written.
222
223       Details  of  the  individual slave or master design are hidden behind a
224       consistent interface. The goal is to provide an easy set of tools for a
225       software  designer  to create monitoring or control applications. There
226       are some performance enhancements in the implementation, including data
227       caching, parallel access to bus masters, and aggregation of device com‐
228       munication. Still the fundamental goal has been ease of use,  flexibil‐
229       ity and correctness rather than speed.
230
231   DS2751
232       The  DS2751  (3)  is battery charging controllers similar to the DS2760
233       [1m(3)
234
235       A number of interesting devices can be built with the  DS2751  (3)  in‐
236       cluding  thermocouples.  Support  for  thermocouples  in built into the
237       software, using the embedded thermister as the cold  junction  tempera‐
238       ture.
239

ADDRESSING

241       All  1-wire  devices are factory assigned a unique 64-bit address. This
242       address is of the form:
243
244       Family Code
245              8 bits
246
247       Address
248              48 bits
249
250       CRC    8 bits
251
252       Addressing under OWFS is in hexadecimal, of form:
253
254              01.123456789ABC
255
256       where 01 is an example 8-bit family code, and 12345678ABC is an example
257       48 bit address.
258
259       The  dot  is  optional,  and the CRC code can included. If included, it
260       must be correct.
261

DATASHEET

263       http://pdfserv.maxim-ic.com/en/ds/DS2751.pdf
264

AVAILABILITY

327       http://www.owfs.org
328

AUTHOR

330       Paul Alfille (paul.alfille@gmail.com)
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334OWFS Manpage                         2003                            DS2751(3)