1DS2890(3)                    One-Wire File System                    DS2890(3)
2
3
4

NAME

6       DS2890 - 1-Wire Digital Potentiometer
7

SYNOPSIS

9       Variable resistance
10
11       2C  [.]XXXXXXXXXXXX[XX][/[  chargepump  | wiper | address | crc8 | id |
12       locator | r_address | r_id | r_locator | type ]]
13

FAMILY CODE

15       2C
16

SPECIAL PROPERTIES

18   chargepump
19       read-write, yes-no
20       State of the chargepump in the chip (0 = off 1 = on). Only available if
21       external  power  is available (hence not in the TO-92 packaging) at pin
22       Vdd.
23       When chargepump is on, the wiper resistance will range between  Rh  and
24       Rl relatively linearly.
25       When  chargepump  is  off,  the wiper resistance (to ground) will range
26       relatively linearly (to 100kOhms).
27
28   wiper
29       read-write, unsigned integer
30       Value of the variable element, 0 to 255. The actual  interpretation  of
31       wiper  depands on the chargepump state, but in general 0 is low and 255
32       is high.
33

STANDARD PROPERTIES

35   address
36   r_address
37       read-only, ascii
38       The entire 64-bit unique ID. Given as  upper  case  hexadecimal  digits
39       (0-9A-F).
40       address starts with the family code
41       r address is the address in reverse order, which is often used in other
42       applications and labeling.
43
44   crc8
45       read-only, ascii
46       The 8-bit error correction portion. Uses cyclic redundancy check.  Com‐
47       puted  from the preceding 56 bits of the unique ID number. Given as up‐
48       per case hexadecimal digits (0-9A-F).
49
50   family
51       read-only, ascii
52       The 8-bit family code. Unique to each type of device.  Given  as  upper
53       case hexadecimal digits (0-9A-F).
54
55   id
56   r_id
57       read-only, ascii
58       The 48-bit middle portion of the unique ID number. Does not include the
59       family code or CRC. Given as upper case hexadecimal digits (0-9A-F).
60       r id is the id in reverse order, which is often used in other  applica‐
61       tions and labeling.
62
63   locator
64   r_locator
65       read-only, ascii
66       Uses  an  extension  of the 1-wire design from iButtonLink company that
67       associated 1-wire physical connections with a unique  1-wire  code.  If
68       the  connection is behind a Link Locator the locator will show a unique
69       8-byte number (16 character hexadecimal) starting with family code FE.
70       If no Link Locator is between the device and the  master,  the  locator
71       field will be all FF.
72       r locator is the locator in reverse order.
73
74   present (DEPRECATED)
75       read-only, yes-no
76       Is the device currently present on the 1-wire bus?
77
78   type
79       read-only, ascii
80       Part  name  assigned by Dallas Semi. E.g.  DS2401 Alternative packaging
81       (iButton vs chip) will not be distiguished.
82

ALARMS

84       The device condition that will cause individual DS2890s to  participate
85       in a Conditional Search is a wiper position located at the power-on de‐
86       fault setting (00h). This feature enables the bus master to easily  de‐
87       termine  whether  a potentiometer has gone through a power-on reset and
88       needs to be re-configured with a required wiper position setting.
89

DESCRIPTION

91   1-Wire
92       1-wire is a wiring protocol and series of devices designed and manufac‐
93       tured  by  Dallas  Semiconductor, Inc. The bus is a low-power low-speed
94       low-connector scheme where the data line can also provide power.
95
96       Each device is uniquely and unalterably  numbered  during  manufacture.
97       There  are a wide variety of devices, including memory, sensors (humid‐
98       ity, temperature, voltage, contact, current), switches, timers and data
99       loggers.  More complex devices (like thermocouple sensors) can be built
100       with these basic devices. There are also 1-wire devices that  have  en‐
101       cryption included.
102
103       The  1-wire  scheme uses a single bus master and multiple slaves on the
104       same wire. The bus master initiates all communication. The  slaves  can
105       be individually discovered and addressed using their unique ID.
106
107       Bus  masters come in a variety of configurations including serial, par‐
108       allel, i2c, network or USB adapters.
109
110   OWFS design
111       OWFS is a suite of programs that designed to make the  1-wire  bus  and
112       its  devices easily accessible. The underlying principle is to create a
113       virtual filesystem, with the unique ID being the directory, and the in‐
114       dividual  properties of the device are represented as simple files that
115       can be read and written.
116
117       Details of the individual slave or master design are  hidden  behind  a
118       consistent interface. The goal is to provide an easy set of tools for a
119       software designer to create monitoring or control  applications.  There
120       are some performance enhancements in the implementation, including data
121       caching, parallel access to bus masters, and aggregation of device com‐
122       munication.  Still the fundamental goal has been ease of use, flexibil‐
123       ity and correctness rather than speed.
124
125   DS2890
126       The D2890 (3) allows variable resistance under 1-wire control. Possible
127       uses are analog feedback mechanisms (sound pitch, light level).
128
129       Although  there  are  provisions  in the datasheet for different DS2890
130       configurations (non-linear wiper ranges, multiple wipers, different re‐
131       sistance  scales)  non  are  in production. To simplify implementation,
132       this driver assumes the standard DS2890 design.
133

ADDRESSING

135       All 1-wire devices are factory assigned a unique 64-bit  address.  This
136       address is of the form:
137
138       Family Code
139              8 bits
140
141       Address
142              48 bits
143
144       CRC    8 bits
145
146       Addressing under OWFS is in hexadecimal, of form:
147
148              01.123456789ABC
149
150       where 01 is an example 8-bit family code, and 12345678ABC is an example
151       48 bit address.
152
153       The dot is optional, and the CRC code can  included.  If  included,  it
154       must be correct.
155

DATASHEET

157       http://pdfserv.maxim-ic.com/en/ds/DS2890.pdf
158

SEE ALSO

160   Programs
161       owfs  (1)  owhttpd  (1)  owftpd  (1)  owserver (1) owdir (1) owread (1)
162       owwrite (1) owpresent (1) owtap (1)
163
164   Configuration and testing
165       owfs (5) owtap (1) owmon (1)
166
167   Language bindings
168       owtcl (3) owperl (3) owcapi (3)
169
170   Clocks
171       DS1427 (3) DS1904 (3) DS1994 (3) DS2404  (3)  DS2404S  (3)  DS2415  (3)
172       DS2417 (3)
173
174   ID
175       DS2401 (3) DS2411 (3) DS1990A (3)
176
177   Memory
178       DS1982  (3)  DS1985  (3)  DS1986  (3)  DS1991 (3) DS1992 (3) DS1993 (3)
179       DS1995 (3) DS1996 (3) DS2430A (3) DS2431  (3)  DS2433  (3)  DS2502  (3)
180       DS2506 (3) DS28E04 (3) DS28EC20 (3)
181
182   Switches
183       DS2405 (3) DS2406 (3) DS2408 (3) DS2409 (3) DS2413 (3) DS28EA00 (3) In‐
184       fernoEmbedded (3)
185
186   Temperature
187       DS1822 (3) DS1825 (3) DS1820 (3) DS18B20 (3)  DS18S20  (3)  DS1920  (3)
188       DS1921  (3) DS1821 (3) DS28EA00 (3) DS28E04 (3) EDS0064 (3) EDS0065 (3)
189       EDS0066 (3) EDS0067 (3) EDS0068 (3) EDS0071 (3)  EDS0072  (3)  MAX31826
190       (3)
191
192   Humidity
193       DS1922 (3) DS2438 (3) EDS0065 (3) EDS0068 (3)
194
195   Voltage
196       DS2450 (3)
197
198   Resistance
199       DS2890 (3)
200
201   Multifunction (current, voltage, temperature)
202       DS2436  (3)  DS2437  (3)  DS2438  (3)  DS2751 (3) DS2755 (3) DS2756 (3)
203       DS2760 (3) DS2770 (3) DS2780 (3) DS2781 (3) DS2788 (3) DS2784 (3)
204
205   Counter
206       DS2423 (3)
207
208   LCD Screen
209       LCD (3) DS2408 (3)
210
211   Crypto
212       DS1977 (3)
213
214   Pressure
215       DS2406 (3) TAI8570 (3) EDS0066 (3) EDS0068 (3)
216
217   Moisture
218       EEEF (3) DS2438 (3)
219

AVAILABILITY

221       http://www.owfs.org
222

AUTHOR

224       Paul Alfille (paul.alfille@gmail.com)
225
226
227
228OWFS Manpage                         2003                            DS2890(3)
Impressum