DS2755(3)

1DS2755(3)                    One-Wire File System                    DS2755(3)
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3
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NAME

6       DS2755, DS2756 - Multichemistry Battery Fuel Gauge
7

SYNOPSIS

9   Temperature Voltage, Current, Memory, and Switch.
10       35 [.]XXXXXXXXXXXX[XX][/[ alarm_set/[volthigh|voltlow|temphigh|templow]
11       | lock.[0-2|ALL] | memory | pages/page.[0-2|ALL] | PIO | sensed |  tem‐
12       perature | vbias | vis | volt | volthours |
13       defaultpmod  |  pie0  |  pie1 | rnaop | ios | uben | ovd | pmod | por |
14       uven |
15       address | crc8 | id | locator | r_address | r_id | r_locator | type ]]
16
17   Thermocouple
18       35   [.]XXXXXXXXXXXX[XX][/[    temperature    |    typeX/range_low    |
19       typeX/range_high | typeX/temperature
20

FAMILY CODE

22       35
23

SPECIAL PROPERTIES

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

THERMOCOUPLE

99   typeX/
100       directory
101       Thermocouple  circuit  using the DS2755 to read the Seebeck voltage and
102       the reference temperature. Since the type interpretation of the  values
103       read depends on the type of thermocouple, the correct directory must be
104       chosen. Supported thermocouple types include types B, E, J, K, N, R,  S
105       and T.
106
107   typeX/range_low typeX/ranges_high
108       read-only, flaoting point
109       The  lower  and  upper  temperature  supported by this thermocouple (at
110       least by the conversion routines). In the globally  chosen  temperature
111       units.
112
113   typeX/temperature
114       read-only, floating point
115       Thermocouple  temperature.  Requires  a voltage and temperature conver‐
116       sion. Returned in globally chosen temperature units.
117       Note: there are two types of  temperature  measurements  possible.  The
118       temperature value in the main device directory is the reference temper‐
119       ature read at the chip. The typeX/temperature value is at  the  thermo‐
120       couple junction, probably remote from the chip.
121

OBSCURE PROPERTIES

123   pmod por uven pie0 pie1 ios uben ovd rnaop
124       varies, yes-no
125       Bit  flags corresponding to various battery management functions of the
126       chip. See the DATASHEET for details of the identically named entries.
127       In general, writing "0" corresponds to a 0 bit value, and non-zero cor‐
128       responds to a 1 bit value.
129
130   defaultpmod
131       read-write, yes-no
132       Default power-on state for the corresponding properties.
133

STANDARD PROPERTIES

135   address
136   r_address
137       read-only, ascii
138       The  entire  64-bit  unique  ID. Given as upper case hexadecimal digits
139       (0-9A-F).
140       address starts with the family code
141       r address is the address in reverse order, which is often used in other
142       applications and labeling.
143
144   crc8
145       read-only, ascii
146       The  8-bit error correction portion. Uses cyclic redundancy check. Com‐
147       puted from the preceding 56 bits of the unique ID number. Given as  up‐
148       per case hexadecimal digits (0-9A-F).
149
150   family
151       read-only, ascii
152       The  8-bit  family  code. Unique to each type of device. Given as upper
153       case hexadecimal digits (0-9A-F).
154
155   id
156   r_id
157       read-only, ascii
158       The 48-bit middle portion of the unique ID number. Does not include the
159       family code or CRC. Given as upper case hexadecimal digits (0-9A-F).
160       r  id is the id in reverse order, which is often used in other applica‐
161       tions and labeling.
162
163   locator
164   r_locator
165       read-only, ascii
166       Uses an extension of the 1-wire design from  iButtonLink  company  that
167       associated  1-wire  physical  connections with a unique 1-wire code. If
168       the connection is behind a Link Locator the locator will show a  unique
169       8-byte number (16 character hexadecimal) starting with family code FE.
170       If  no  Link  Locator is between the device and the master, the locator
171       field will be all FF.
172       r locator is the locator in reverse order.
173
174   present (DEPRECATED)
175       read-only, yes-no
176       Is the device currently present on the 1-wire bus?
177
178   type
179       read-only, ascii
180       Part name assigned by Dallas Semi. E.g.  DS2401  Alternative  packaging
181       (iButton vs chip) will not be distiguished.
182

ALARMS

184       Temperature and voltage.
185

DESCRIPTION

187   1-Wire
188       1-wire is a wiring protocol and series of devices designed and manufac‐
189       tured by Dallas Semiconductor, Inc. The bus is  a  low-power  low-speed
190       low-connector scheme where the data line can also provide power.
191
192       Each  device  is  uniquely and unalterably numbered during manufacture.
193       There are a wide variety of devices, including memory, sensors  (humid‐
194       ity, temperature, voltage, contact, current), switches, timers and data
195       loggers. More complex devices (like thermocouple sensors) can be  built
196       with  these  basic devices. There are also 1-wire devices that have en‐
197       cryption included.
198
199       The 1-wire scheme uses a single bus master and multiple slaves  on  the
200       same  wire.  The bus master initiates all communication. The slaves can
201       be individually discovered and addressed using their unique ID.
202
203       Bus masters come in a variety of configurations including serial,  par‐
204       allel, i2c, network or USB adapters.
205
206   OWFS design
207       OWFS  is  a  suite of programs that designed to make the 1-wire bus and
208       its devices easily accessible. The underlying principle is to create  a
209       virtual filesystem, with the unique ID being the directory, and the in‐
210       dividual properties of the device are represented as simple files  that
211       can be read and written.
212
213       Details  of  the  individual slave or master design are hidden behind a
214       consistent interface. The goal is to provide an easy set of tools for a
215       software  designer  to create monitoring or control applications. There
216       are some performance enhancements in the implementation, including data
217       caching, parallel access to bus masters, and aggregation of device com‐
218       munication. Still the fundamental goal has been ease of use,  flexibil‐
219       ity and correctness rather than speed.
220
221   DS2755 DS2756
222       The  DS2755 (3) and DS2756 (3) are battery charging controllers similar
223       to the DS2751 (3) except no internal resistor option and a larger  EEP‐
224       ROM memory.
225
226       The DS2756 (3) adds suspend modes ( pie0 pie1 ) to the DS2755 (3)
227
228       A  number  of  interesting devices can be built with the DS2755 (3) and
229       DS2756 (3) including thermocouples. Support for thermocouples in  built
230       into  the  software, using the embedded thermister as the cold junction
231       temperature.
232

ADDRESSING

234       All 1-wire devices are factory assigned a unique 64-bit  address.  This
235       address is of the form:
236
237       Family Code
238              8 bits
239
240       Address
241              48 bits
242
243       CRC    8 bits
244
245       Addressing under OWFS is in hexadecimal, of form:
246
247              01.123456789ABC
248
249       where 01 is an example 8-bit family code, and 12345678ABC is an example
250       48 bit address.
251
252       The dot is optional, and the CRC code can  included.  If  included,  it
253       must be correct.
254

DATASHEET

256       http://pdfserv.maxim-ic.com/en/ds/DS2755.pdf
257       http://pdfserv.maxim-ic.com/en/ds/DS2756.pdf
258

AVAILABILITY

321       http://www.owfs.org
322

AUTHOR

324       Paul Alfille (paul.alfille@gmail.com)
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328OWFS Manpage                         2003                            DS2755(3)