1DS2438(3)                    One-Wire File System                    DS2438(3)
2
3
4

NAME

6       DS2438 - Smart Battery Monitor
7

SYNOPSIS

9   Temperature Voltages and Current.
10       26  [.]XXXXXXXXXXXX[XX][/[  CA  | EE | date | disconnect/date | discon‐
11       nect/udate  |  endcharge/date  |  endcharge/udate  |  IAD  |  offset  |
12       pages/page.[0-7|ALL]  |  temperature | latesttemp | udate | VAD | VDD |
13       vis | address | crc8 | id | locator | r_address | r_id  |  r_locator  |
14       type ]]
15
16   Humidity sensor
17       26   [.]XXXXXXXXXXXX[XX][/[   HIH4000/humidity   |  HIH5030/humidity  |
18       HTM1735/humidity | DATANAB/reset | DATANAB/humidity | humidity  |  tem‐
19       perature ]]
20
21   Barometer
22       26    [.]XXXXXXXXXXXX[XX][/[    B1-R1-A/pressure   |   B1-R1-A/gain   |
23       B1-R1-A/offset | ]]
24
25   Light
26       26  [.]XXXXXXXXXXXX[XX][/[  S3-R1-A/current  |  S3-R1-A/illuminance   |
27       S3-R1-A/gain ]]
28

FAMILY CODE

30       26
31

SPECIAL PROPERTIES

33   pages/page.0 ... pages/page.7 pages/page.ALL
34       read-write, binary
35       Memory  is  split  into 8 pages of 8 bytes each. Only the pages 3-7 are
36       really available, and some of that appears  to  be  reserved.  See  the
37       datasheet for details.
38       ALL is an aggregate of the pages. Each page is accessed sequentially.
39
40   temperature
41       read-only, floating point
42       Temperature  read  by the chip at high resolution (~13 bits). Units are
43       selected from the invoking command line. See owfs(1) or owhttpd(1)  for
44       choices. Default is Celsius.  Conversion takes ~20 msec.
45
46   latesttemp
47       read-only, floating point
48       Latest  measured  temperature.  Reading  this node will never trigger a
49       temperature conversion. Intended for use in conjunction with  /simulta‐
50       neous/temperature.
51
52   VAD VDD
53       read-only, floating point
54       Voltage  read  (~10 bits) at the one of the chip's two supply voltages.
55       Range VDD= 2.4V to 10V, VAD=1.5 to 10V.
56
57   vis
58       read-only, floating point
59       Current sensor reading, as a voltage difference. Value is in volts.
60       Actual current depends on Rsens resistor (see datasheet).
61       The formula for current is I = vis / Rsens
62       with units in Amps and Ohms.
63       Current measurement will be temporarily enabled (see Ienable )  if  not
64       currently enabled (pun intended) for this reading.
65

CONFIGURATION PROPERTIES

67   CA
68       read-write, yes-no
69       Current  Accumulator  Configuration  flag  bit.  If "on" (1) current is
70       stored in page 7 bytes 4-7. If "off" (0) that page can be used for gen‐
71       eral storage. See the datasheet for more information.
72
73   EE
74       read-write, yes-no
75       Current  Accumulator  Shadow  flag  bit. If "on" (1) current reading is
76       stored to EEPROM. If "off" (0) that data will be lost when  chip  loses
77       power. See the datasheet for more information
78
79   IAD
80       read-write, yes-no
81       Current A/D Control flag bit. If "on" (1) current measured at 36.41 Hz.
82       If "off" (0) current measurements won't be made. See the datasheet  for
83       more information.
84

DATE PROPERTIES

86   date
87       read-write, ascii
88       26  character date representation of the counter value. Increments once
89       per second.
90       Setting date to a null string will put the current system time.
91       Accepted date formats are:
92         Sat[urday] March 12 12:23:59 2001
93         Apr[il] 4 9:34:56 2002
94         3/23/04 23:34:57
95         current locale setting (your system's format)
96
97   disconnect/date
98       read-write, ascii
99       26 character date representation of the  disconnect/udate  value.  Time
100       when the battery pack waws removed from the charger. Format is the same
101       as the date property.
102
103   disconnect/udate
104       read-write, unsigned integer
105       Representation of disconnect/date as a number. See udate for details.
106
107   endcharge/date
108       read-write, ascii
109       26 character date representation of the endcharge/udate  value.  Format
110       is the same as the date property.
111
112   endcharge/udate
113       read-write, unsigned integer
114       Representation of endcharge/date as a number. See udate for details.
115
116   udate
117       read-write, unsigned integer
118       Time represented as a number.  udate increments once per second.
119       Usually set to unix time standard: number of seconds since Jan 1, 1970.
120       The date field will be the unix representation (ascii  text)  of  udate
121       and setting either will change the other.
122

HUMIDITY PROPERTIES

124   HIH4000/humidity
125       read-only, floating point
126       Relative humidity, as percent (1-100 scale).
127       This  value is for a design based on Honeywell's HIH-4000 humidity sen‐
128       sor.
129
130   HIH5030/humidity
131       read-only, floating point
132       Relative humidity, as percent (1-100 scale).
133       This value is for a design based on Honeywell's HIH-5030/5031  humidity
134       sensor.
135
136   HTM1735/humidity
137       read-only, floating point
138       Relative humidity, as percent (1-100 scale).
139       This value is for a design based on Humirel's HTM-1735 humidity sensor.
140
141   DATANAB/humidity
142       read-only, floating point
143       Based  on  DataNAB's humidity sensor. It uses a HIH-4000 sensor and the
144       current sensning rather than voltage readings from the DS2438. Calibra‐
145       tion  values  are  stored  on chip, and a check field is stored in chip
146       memory.
147
148   DATANAB/reset
149       write-only, yes-no
150       Used to read calibration values and set the  chip  to  current  reading
151       more.  Should  be  automatically  called when a humidity reading is re‐
152       quested.
153
154   humidity
155       read-only, floating point
156       Relative humidity, as percent (1-100 scale).
157       The DS2438 actually does not read humidity, but a widely available  and
158       publicised circuit based on the chip, does. This design is for the com‐
159       mon Honeywell HIH-3610 humidity chip. The  mostly  compatible  HIH-4000
160       chip  uses  different  temperature compensation, so is better read from
161       the HIH4000/humidity value. See the datasheets for details.
162       If the chip is instead a DATANAB  design,  the  DATANAB/humidity  value
163       will be automatically used.
164

BAROMETER PROPERTIES

166   B1-R1-A/pressure
167       read-only, floating point
168       Pressure  reading,  as  milli-bars,  or  other  unit  depending on set‐
169       tings/units/pressure_scale.
170       This value is for the B1-R1-A barometer from Hobby-Boards, and  assumes
171       the standard calibration.
172
173   B1-R1-A/gain
174       read/write, floating point
175       Calibration  of  pressure gain, as signed number, expressed as the same
176       units as B1-R1-A/pressure per volt.
177       This value will be multiplied with the  measured  voltage  to  get  the
178       B1-R1-A/pressure  reading. It may have to be fine tuned for calibration
179       purposes, although with the standard sensor,  it  will  often  be  good
180       enough to keep it as is.
181
182   B1-R1-A/offset
183       read/write, floating point
184       Calibration  of  pressure  offset,  as  signed  number,  same  units as
185       B1-R1-A/pressure.
186       This value will be added to the B1-R1-A/pressure reading.  The  default
187       value is 904.7 millibars, which may be altered to to compensate for el‐
188       evation.
189

SOLAR SENSOR PROPERTIES

191   S3-R1-A/current
192       read-only, floating point
193       Photo-diode current, in micro-amperes.
194       This value is for the S3-R1-A solar radiation sensor from Hobby-Boards.
195       Due  to  noise and offsets, this value may read as a negative number in
196       low light conditions.  The offset register can be  modified  to  reduce
197       the offset as much as possible.
198
199   S3-R1-A/illumination
200       read-only, floating point
201       Illumination, in lux. Always a positive number.
202       This   value   is  the  lux  reading  from  the  solar  sensor,  taking
203       S3-R1-A/gain into consideration.
204
205   S3-R1-A/gain
206       read/write, floating point
207       Calibration of photo-diode gain expressed  as  lux  per  micro-amperes.
208       The default value is for the SFH203P photo-diode from Osram, used bare.
209       A different gain may be used for instance to compensate  for  an  inte‐
210       grathing, white sphere placed over the diode.
211       This value is for the S3-R1-A solar radiation sensor from Hobby-Boards,
212       using the SFH203P photo-diode from Osram.
213

MULTISENSOR PROPERTIES

215   MultiSensor/type
216       read-only, ascii
217       For iButtonLink's MultiSensor line of 1-wire devices, give the specific
218       configuration  based  on a data byte set in memory. (Byte 0 of page 3).
219       This can help interpretation of the sensor values, distinguishing, cur‐
220       rent from water from light.
221
222   offset
223       read-write, integer
224       Correction  for current readings. A value between -256 and 255. See the
225       datasheet for details. Should be set to the negative  of  a  true  zero
226       current reading.
227

STANDARD PROPERTIES

229   address
230   r_address
231       read-only, ascii
232       The  entire  64-bit  unique  ID. Given as upper case hexadecimal digits
233       (0-9A-F).
234       address starts with the family code
235       r address is the address in reverse order, which is often used in other
236       applications and labeling.
237
238   crc8
239       read-only, ascii
240       The  8-bit error correction portion. Uses cyclic redundancy check. Com‐
241       puted from the preceding 56 bits of the unique ID number. Given as  up‐
242       per case hexadecimal digits (0-9A-F).
243
244   family
245       read-only, ascii
246       The  8-bit  family  code. Unique to each type of device. Given as upper
247       case hexadecimal digits (0-9A-F).
248
249   id
250   r_id
251       read-only, ascii
252       The 48-bit middle portion of the unique ID number. Does not include the
253       family code or CRC. Given as upper case hexadecimal digits (0-9A-F).
254       r  id is the id in reverse order, which is often used in other applica‐
255       tions and labeling.
256
257   locator
258   r_locator
259       read-only, ascii
260       Uses an extension of the 1-wire design from  iButtonLink  company  that
261       associated  1-wire  physical  connections with a unique 1-wire code. If
262       the connection is behind a Link Locator the locator will show a  unique
263       8-byte number (16 character hexadecimal) starting with family code FE.
264       If  no  Link  Locator is between the device and the master, the locator
265       field will be all FF.
266       r locator is the locator in reverse order.
267
268   present (DEPRECATED)
269       read-only, yes-no
270       Is the device currently present on the 1-wire bus?
271
272   type
273       read-only, ascii
274       Part name assigned by Dallas Semi. E.g.  DS2401  Alternative  packaging
275       (iButton vs chip) will not be distiguished.
276

ALARMS

278       None.
279

DESCRIPTION

281   1-Wire
282       1-wire is a wiring protocol and series of devices designed and manufac‐
283       tured by Dallas Semiconductor, Inc. The bus is  a  low-power  low-speed
284       low-connector scheme where the data line can also provide power.
285
286       Each  device  is  uniquely and unalterably numbered during manufacture.
287       There are a wide variety of devices, including memory, sensors  (humid‐
288       ity, temperature, voltage, contact, current), switches, timers and data
289       loggers. More complex devices (like thermocouple sensors) can be  built
290       with  these  basic devices. There are also 1-wire devices that have en‐
291       cryption included.
292
293       The 1-wire scheme uses a single bus master and multiple slaves  on  the
294       same  wire.  The bus master initiates all communication. The slaves can
295       be individually discovered and addressed using their unique ID.
296
297       Bus masters come in a variety of configurations including serial,  par‐
298       allel, i2c, network or USB adapters.
299
300   OWFS design
301       OWFS  is  a  suite of programs that designed to make the 1-wire bus and
302       its devices easily accessible. The underlying principle is to create  a
303       virtual filesystem, with the unique ID being the directory, and the in‐
304       dividual properties of the device are represented as simple files  that
305       can be read and written.
306
307       Details  of  the  individual slave or master design are hidden behind a
308       consistent interface. The goal is to provide an easy set of tools for a
309       software  designer  to create monitoring or control applications. There
310       are some performance enhancements in the implementation, including data
311       caching, parallel access to bus masters, and aggregation of device com‐
312       munication. Still the fundamental goal has been ease of use,  flexibil‐
313       ity and correctness rather than speed.
314
315   DS2438
316       The DS2438 (3) is a more complete form of the DS2436 battery chip. Cur‐
317       rent sensing is available, but not  implemented.  The  major  advantage
318       compared  to  the DS2436 is that two voltages can be read, allowing one
319       to correct circuit measurements for supply voltage and  temperature.  A
320       better comparison is the DS276x family of chips.
321

ADDRESSING

323       All  1-wire  devices are factory assigned a unique 64-bit address. This
324       address is of the form:
325
326       Family Code
327              8 bits
328
329       Address
330              48 bits
331
332       CRC    8 bits
333
334       Addressing under OWFS is in hexadecimal, of form:
335
336              01.123456789ABC
337
338       where 01 is an example 8-bit family code, and 12345678ABC is an example
339       48 bit address.
340
341       The  dot  is  optional,  and the CRC code can included. If included, it
342       must be correct.
343

DATASHEET

345       http://pdfserv.maxim-ic.com/en/ds/DS2438.pdf
346       http://pdfserv.maxim-ic.com/en/an/humsensor.pdf
347       http://goo.gl/o9DH0 (Redirects  to  009012_2.pdf  PDF  file  on  honey‐
348       well.com website)
349       http://www.phanderson.com/hih-4000.pdf
350       http://www.humirel.com/product/fichier/HTM1735%20RevG%20.pdf
351

SEE ALSO

353   Programs
354       owfs  (1)  owhttpd  (1)  owftpd  (1)  owserver (1) owdir (1) owread (1)
355       owwrite (1) owpresent (1) owtap (1)
356
357   Configuration and testing
358       owfs (5) owtap (1) owmon (1)
359
360   Language bindings
361       owtcl (3) owperl (3) owcapi (3)
362
363   Clocks
364       DS1427 (3) DS1904 (3) DS1994 (3) DS2404  (3)  DS2404S  (3)  DS2415  (3)
365       DS2417 (3)
366
367   ID
368       DS2401 (3) DS2411 (3) DS1990A (3)
369
370   Memory
371       DS1982  (3)  DS1985  (3)  DS1986  (3)  DS1991 (3) DS1992 (3) DS1993 (3)
372       DS1995 (3) DS1996 (3) DS2430A (3) DS2431  (3)  DS2433  (3)  DS2502  (3)
373       DS2506 (3) DS28E04 (3) DS28EC20 (3)
374
375   Switches
376       DS2405 (3) DS2406 (3) DS2408 (3) DS2409 (3) DS2413 (3) DS28EA00 (3) In‐
377       fernoEmbedded (3)
378
379   Temperature
380       DS1822 (3) DS1825 (3) DS1820 (3) DS18B20 (3)  DS18S20  (3)  DS1920  (3)
381       DS1921  (3) DS1821 (3) DS28EA00 (3) DS28E04 (3) EDS0064 (3) EDS0065 (3)
382       EDS0066 (3) EDS0067 (3) EDS0068 (3) EDS0071 (3)  EDS0072  (3)  MAX31826
383       (3)
384
385   Humidity
386       DS1922 (3) DS2438 (3) EDS0065 (3) EDS0068 (3)
387
388   Voltage
389       DS2450 (3)
390
391   Resistance
392       DS2890 (3)
393
394   Multifunction (current, voltage, temperature)
395       DS2436  (3)  DS2437  (3)  DS2438  (3)  DS2751 (3) DS2755 (3) DS2756 (3)
396       DS2760 (3) DS2770 (3) DS2780 (3) DS2781 (3) DS2788 (3) DS2784 (3)
397
398   Counter
399       DS2423 (3)
400
401   LCD Screen
402       LCD (3) DS2408 (3)
403
404   Crypto
405       DS1977 (3)
406
407   Pressure
408       DS2406 (3) TAI8570 (3) EDS0066 (3) EDS0068 (3)
409
410   Moisture
411       EEEF (3) DS2438 (3)
412

AVAILABILITY

414       http://www.owfs.org
415

AUTHOR

417       Paul Alfille (paul.alfille@gmail.com) Egil Kvaleberg
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421OWFS Manpage                         2003                            DS2438(3)
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