DS2450(3)

1DS2450(3)                    One-Wire File System                    DS2450(3)
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NAME

6       DS2450 - Quad A/D Converter
7

SYNOPSIS

9   Voltage * 4 and Memory.
10       20  [.]XXXXXXXXXXXX[XX][/[  PIO.[A-D|ALL]  | volt.[A-D|ALL] | volt2.[A-
11       D|ALL] | latestvolt.[A-D|ALL] | latestvolt2.[A-D|ALL] ]]
12
13       20 [.]XXXXXXXXXXXX[XX][/[ 8bit/volt.[A-D|ALL] | 8bit/volt2.[A-D|ALL]  |
14       8bit/latestvolt.[A-D|ALL] | 8bit/latestvolt2.[A-D|ALL] ]]
15
16       20 [.]XXXXXXXXXXXX[XX][/[ memory | pages/page.[0-3|ALL] | power ]
17
18       20  [.]XXXXXXXXXXXX[XX][/[ alarm/high.[A-D|ALL] | alarm/low.[A-D|ALL] |
19       set_alarm/high.[A-D|ALL] | set_alarm/low.[A-D|ALL] | set_alarm/unset  |
20       set_alarm/volthigh.[A-D|ALL]    |    set_alarm/volt2high.[A-D|ALL]    |
21       set_alarm/voltlow.[A-D|ALL] | set_alarm/volt2low.[A-D|ALL] ]
22
23       20 [.]XXXXXXXXXXXX[XX][/[ address | crc8 | id | locator |  r_address  |
24       r_id | r_locator | type ]]
25
26   CO2 sensor
27       20 [.]XXXXXXXXXXXX[XX][/[ CO2/ppm | CO2/power | CO2/status ]
28

FAMILY CODE

30       20
31

SPECIAL PROPERTIES

33   alarm/high.A ... alarm/high.D alarm.high.ALL
34   alarm/high.A ... alarm/high.D alarm.high.ALL
35       read-write, binary
36       The  alarm  state of the voltage channel. The alarm state is set one of
37       two ways:
38
39       voltage conversion
40              Whenever the DS2450 measures a voltage on a channel, that  volt‐
41              age  is  compared  to the high and low limits set_alarm/volthigh
42              and/or  set_alarm/voltlow  and   if   the   alarm   is   enabled
43              set_alarm/high  and/or  set_alarm/low  the corresponding flag is
44              set in alarm/high and/or alarm/low
45
46       manual set
47              The flag can be set by a direct write to alarm/high or alarm/low
48
49   memory
50       read-write, binary
51       32 bytes of data. Much has special implications. See the datasheet.
52
53   pages/page.0 ... pages/page.3 pages/page.ALL
54       read-write, binary
55       Memory is split into 4 pages of 8 bytes each. Mostly  for  reading  and
56       setting device properties. See the datasheet for details.
57       ALL is an aggregate of the pages. Each page is accessed sequentially.
58
59   PIO.A ... PIO.D PIO.ALL
60       read-write, yes-no
61       Pins  used  for  digital control. 1 turns the switch on (conducting). 0
62       turns the switch off (non-conducting).
63       Control is specifically enabled. Reading volt will turn off  this  con‐
64       trol.
65       ALL is an aggregate of the voltages. Readings are made separately.
66
67   power
68       read-write, yes-no
69       Configure whether the DS2450 is externally powered (as opposed to para‐
70       sitically powered from the data line).
71       If configured as powered, the A/D coverter will be  set  to  continuous
72       sampling,  and  the bus will be released during a single conversion al‐
73       lowing other devices to communicate.
74       Setting this to 1 when no power is applied to the chip's Vcc  will  re‐
75       sult  in  wrong  voltage readouts.  Setting this to 0 when power is ap‐
76       plied to the chip's Vcc allows a simultaneous conversion trigger on all
77       DS2450 on a bus. The (always safe) default is 0.
78
79   set_alarm/high.A ... set_alarm/high.D set_alarm/high.ALL
80   set_alarm/low.A ... set_alarm/low.D set_alarm/low.ALL
81       read-write, yes-no
82       Enabled status of the voltage threshold. 1 is on. 0 is off.
83
84   set_alarm/volthigh.A ... set_alarm/volthigh.D set_alarm/volthigh.ALL
85   set_alarm/volt2high.A ... set_alarm/volt2high.D set_alarm/volt2high.ALL
86   set_alarm/voltlow.A ... set_alarm/voltlow.D set_alarm/voltlow.ALL
87   set_alarm/volt2low.A ... set_alarm/volt2low.D set_alarm/volt2low.ALL
88       read-write, floating point
89       The  upper or lower limit for the voltage measured before triggering an
90       alarm.
91       Note that the alarm must be enabled alarm/high or alarm.low and an  ac‐
92       tual  reading must be requested volt for the alarm state to actually be
93       set. The alarm state can be sensed at alarm/high and alarm/low
94
95   set_alarm/unset
96       read-write, yes-no
97       Status of the power-on-reset (POR) flag.
98       The POR is set when the DS2450 is first powered up, and will match  the
99       alarm state until explicitly cleared. (By writing 0 to it).
100       The  purpose  of  the POR is to alert the user that the chip is not yet
101       fully configured, especially alarm thresholds and enabling.
102
103   volt.A ... volt.D volt.ALL
104   volt2.A ... volt2.D volt2.ALL
105   8bit/volt.A ... 8bit/volt.D 8bit/volt.ALL
106   8bit/volt2.A ... 8bit/volt2.D 8bit/volt2.ALL
107       read-only, floating point
108       Reading one of these nodes triggers a conversion on the specified volt‐
109       age input(s) with the selected resolution (16 or 8 bit) and returns the
110       sampled voltage(s) with the selected scaling (0 - 5.10V or 0 -  2.55V).
111       The  conversion  time is about 1.4ms per input for 16-bit and 0.8ms per
112       input for 8-bit.  The output feature ( PIO ) is disabled by reading the
113       corresponding node.
114       ALL is an aggregate of the voltages. Sampling is controlled by the chip
115       and done in the order A, B, C, D, one after another.
116
117   latestvolt.A ... latestvolt.D latestvolt.ALL
118   latestvolt2.A ... latestvolt2.D latestvolt2.ALL
119   8bit/latestvolt.A ... 8bit/latestvolt.D 8bit/latestvolt.ALL
120   8bit/latestvolt2.A ... 8bit/latestvolt2.D 8bit/latestvolt2.ALL
121       read-only, floating point
122       Returns previously measured voltage on the specified input(s) with  the
123       selected  scaling (0 - 5.10V or 0 - 2.55V).  Resolution and scaling are
124       set by sampling a voltage, not here; the correct latestvolt nodes  have
125       to be read to make the result meaningful.
126       ALL is an aggregate of the voltages and returns all voltage values from
127       the chip.
128       Reading these nodes will never trigger a voltage  conversion.  Intended
129       for use in conjunction with /simultaneous/voltage.
130

CO2 (Carbon Dioxide) SENSOR PROPERTIES

132       The CO2 sensor is a device constructed from a SenseAir K30 and a DS2450
133
134   CO2/power
135       read-only, floating point
136       Supply voltage to the CO2 sensor (should be around 5V)
137
138   CO2/ppm
139       read-only, unsigned
140       CO2 level in ppm (parts per million). Range 0-5000.
141
142   CO2/status
143       read-only, yes-no
144       Is the internal voltage correct (around 3.2V)?
145

STANDARD PROPERTIES

147   address
148   r_address
149       read-only, ascii
150       The  entire  64-bit  unique  ID. Given as upper case hexadecimal digits
151       (0-9A-F).
152       address starts with the family code
153       r address is the address in reverse order, which is often used in other
154       applications and labeling.
155
156   crc8
157       read-only, ascii
158       The  8-bit error correction portion. Uses cyclic redundancy check. Com‐
159       puted from the preceding 56 bits of the unique ID number. Given as  up‐
160       per case hexadecimal digits (0-9A-F).
161
162   family
163       read-only, ascii
164       The  8-bit  family  code. Unique to each type of device. Given as upper
165       case hexadecimal digits (0-9A-F).
166
167   id
168   r_id
169       read-only, ascii
170       The 48-bit middle portion of the unique ID number. Does not include the
171       family code or CRC. Given as upper case hexadecimal digits (0-9A-F).
172       r  id is the id in reverse order, which is often used in other applica‐
173       tions and labeling.
174
175   locator
176   r_locator
177       read-only, ascii
178       Uses an extension of the 1-wire design from  iButtonLink  company  that
179       associated  1-wire  physical  connections with a unique 1-wire code. If
180       the connection is behind a Link Locator the locator will show a  unique
181       8-byte number (16 character hexadecimal) starting with family code FE.
182       If  no  Link  Locator is between the device and the master, the locator
183       field will be all FF.
184       r locator is the locator in reverse order.
185
186   present (DEPRECATED)
187       read-only, yes-no
188       Is the device currently present on the 1-wire bus?
189
190   type
191       read-only, ascii
192       Part name assigned by Dallas Semi. E.g.  DS2401  Alternative  packaging
193       (iButton vs chip) will not be distiguished.
194

ALARMS

196       None.
197

DESCRIPTION

199   1-Wire
200       1-wire is a wiring protocol and series of devices designed and manufac‐
201       tured by Dallas Semiconductor, Inc. The bus is  a  low-power  low-speed
202       low-connector scheme where the data line can also provide power.
203
204       Each  device  is  uniquely and unalterably numbered during manufacture.
205       There are a wide variety of devices, including memory, sensors  (humid‐
206       ity, temperature, voltage, contact, current), switches, timers and data
207       loggers. More complex devices (like thermocouple sensors) can be  built
208       with  these  basic devices. There are also 1-wire devices that have en‐
209       cryption included.
210
211       The 1-wire scheme uses a single bus master and multiple slaves  on  the
212       same  wire.  The bus master initiates all communication. The slaves can
213       be individually discovered and addressed using their unique ID.
214
215       Bus masters come in a variety of configurations including serial,  par‐
216       allel, i2c, network or USB adapters.
217
218   OWFS design
219       OWFS  is  a  suite of programs that designed to make the 1-wire bus and
220       its devices easily accessible. The underlying principle is to create  a
221       virtual filesystem, with the unique ID being the directory, and the in‐
222       dividual properties of the device are represented as simple files  that
223       can be read and written.
224
225       Details  of  the  individual slave or master design are hidden behind a
226       consistent interface. The goal is to provide an easy set of tools for a
227       software  designer  to create monitoring or control applications. There
228       are some performance enhancements in the implementation, including data
229       caching, parallel access to bus masters, and aggregation of device com‐
230       munication. Still the fundamental goal has been ease of use,  flexibil‐
231       ity and correctness rather than speed.
232
233   DS2450
234       The  DS2450  (3) is a (supposedly) high resolution A/D converter with 4
235       channels. Actual resolutin is reporterd to be 8 bits. The channels  can
236       also  function  as switches. Voltage sensing (with temperature and cur‐
237       rent, but sometimes restricted voltrage ranges) can  also  be  obtained
238       with the DS2436 , DS2438 and DS276x
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       DS2450 http://pdfserv.maxim-ic.com/en/ds/DS2450.pdf
264
265       CO2 sensor
266              http://www.senseair.se/Datablad/k30%20.pdf
267
268       CO2 device
269              https://www.m.nu/co2meter-version-2-p-259.html?language=en
270

AVAILABILITY

333       http://www.owfs.org
334

AUTHOR

336       Paul Alfille (paul.alfille@gmail.com)
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339
340OWFS Manpage                         2003                            DS2450(3)