1DS2890(3) One-Wire File System DS2890(3)
2
6 DS2890 - 1-Wire Digital Potentiometer
7
9 Variable resistance
10 2C [.]XXXXXXXXXXXX[XX][/[ chargepump | wiper | address | crc8 | id |
12 locator | r_address | r_id | r_locator | type ]]
13
15 2C
16
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 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
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 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 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 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 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 present (DEPRECATED)
75 read-only, yes-no
76 Is the device currently present on the 1-wire bus?
77 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
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
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 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 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 Bus masters come in a variety of configurations including serial, par‐
108 allel, i2c, network or USB adapters.
109 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 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 DS2890
126 The D2890 (3) allows variable resistance under 1-wire control. Possible
127 uses are analog feedback mechanisms (sound pitch, light level).
128 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
135 All 1-wire devices are factory assigned a unique 64-bit address. This
136 address is of the form:
137 Family Code
139 8 bits
140 Address
142 48 bits
143 CRC 8 bits
145 Addressing under OWFS is in hexadecimal, of form:
147 01.123456789ABC
149 where 01 is an example 8-bit family code, and 12345678ABC is an example
151 48 bit address.
152 The dot is optional, and the CRC code can included. If included, it
154 must be correct.
155
157 http://pdfserv.maxim-ic.com/en/ds/DS2890.pdf
158
160 Programs
161 owfs (1) owhttpd (1) owftpd (1) owserver (1) owdir (1) owread (1)
162 owwrite (1) owpresent (1) owtap (1)
163 Configuration and testing
165 owfs (5) owtap (1) owmon (1)
166 Language bindings
168 owtcl (3) owperl (3) owcapi (3)
169 Clocks
171 DS1427 (3) DS1904 (3) DS1994 (3) DS2404 (3) DS2404S (3) DS2415 (3)
172 DS2417 (3)
173 ID
175 DS2401 (3) DS2411 (3) DS1990A (3)
176 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 Switches
183 DS2405 (3) DS2406 (3) DS2408 (3) DS2409 (3) DS2413 (3) DS28EA00 (3) In‐
184 fernoEmbedded (3)
185 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 [1m(3)
191 Humidity
193 DS1922 (3) DS2438 (3) EDS0065 (3) EDS0068 (3)
194 Voltage
196 DS2450 (3)
197 Resistance
199 DS2890 (3)
200 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 Counter
206 DS2423 (3)
207 LCD Screen
209 LCD (3) DS2408 (3)
210 Crypto
212 DS1977 (3)
213 Pressure
215 DS2406 (3) TAI8570 (3) EDS0066 (3) EDS0068 (3)
216 Moisture
218 EEEF (3) DS2438 (3)
219
221 http://www.owfs.org
222
224 Paul Alfille (paul.alfille@gmail.com)
225OWFS Manpage 2003 DS2890(3)