NAME¶
DS2890 - 1-Wire Digital Potentiometer
SYNOPSIS¶
Variable resistance
2C [.]XXXXXXXXXXXX[XX][/[
chargepump |
wiper |
address |
crc8 |
id |
locator |
r_address |
r_id |
r_locator |
type ]]
FAMILY CODE¶
2C
SPECIAL PROPERTIES¶
chargepump¶
read-write, yes-no
State of the
chargepump in the chip (0 = off 1 = on). Only available if
external power is available (hence not in the TO-92 packaging) at pin Vdd.
When
chargepump is on, the
wiper resistance will range between Rh
and Rl relatively linearly.
When
chargepump is off, the
wiper resistance (to ground) will
range relatively linearly (to 100kOhms).
wiper¶
read-write, unsigned integer
Value of the variable element, 0 to 255. The actual interpretation of
wiper depands on the
chargepump state, but in general 0 is low
and 255 is high.
STANDARD PROPERTIES¶
address¶
r_address¶
read-only, ascii
The entire 64-bit unique ID. Given as upper case hexidecimal digits (0-9A-F).
address starts with the
family code
r address is the
address in reverse order, which is often used in
other applications and labeling.
crc8¶
read-only, ascii
The 8-bit error correction portion. Uses cyclic redundancy check. Computed from
the preceding 56 bits of the unique ID number. Given as upper case hexidecimal
digits (0-9A-F).
family¶
read-only, ascii
The 8-bit family code. Unique to each
type of device. Given as upper case
hexidecimal digits (0-9A-F).
r_id¶
read-only, ascii
The 48-bit middle portion of the unique ID number. Does not include the family
code or CRC. Given as upper case hexidecimal digits (0-9A-F).
r id is the
id in reverse order, which is often used in other
applications and labeling.
locator¶
r_locator¶
read-only, ascii
Uses an extension of the 1-wire design from iButtonLink company that associated
1-wire physical connections with a unique 1-wire code. If the connection is
behind a
Link Locator the
locator will show a unique 8-byte number
(16 character hexidecimal) starting with family code FE.
If no
Link Locator is between the device and the master, the
locator field will be all FF.
r locator is the
locator in reverse order.
present (DEPRECATED)¶
read-only, yes-no
Is the device currently
present on the 1-wire bus?
type¶
read-only, ascii
Part name assigned by Dallas Semi. E.g.
DS2401 Alternative packaging
(iButton vs chip) will not be distiguished.
ALARMS¶
The device condition that will cause individual
DS2890s to participate in
a Conditional Search is a wiper position located at the power-on default
setting (00h). This feature enables the bus master to easily determine whether
a potentiometer has gone through a power-on reset and needs to be
re-configured with a required wiper position setting.
DESCRIPTION¶
1-Wire¶
1-wire is a wiring protocol and series of devices designed and
manufactured by Dallas Semiconductor, Inc. The bus is a low-power low-speed
low-connector scheme where the data line can also provide power.
Each device is uniquely and unalterably numbered during manufacture. There are a
wide variety of devices, including memory, sensors (humidity, temperature,
voltage, contact, current), switches, timers and data loggers. More complex
devices (like thermocouple sensors) can be built with these basic devices.
There are also 1-wire devices that have encryption included.
The 1-wire scheme uses a single
bus master and multiple
slaves on
the same wire. The bus master initiates all communication. The slaves can be
individually discovered and addressed using their unique ID.
Bus masters come in a variety of configurations including serial, parallel, i2c,
network or USB adapters.
OWFS design¶
OWFS is a suite of programs that designed to make the 1-wire bus and its
devices easily accessible. The underlying priciple is to create a virtual
filesystem, with the unique ID being the directory, and the individual
properties of the device are represented as simple files that can be read and
written.
Details of the individual slave or master design are hidden behind a consistent
interface. The goal is to provide an easy set of tools for a software designer
to create monitoring or control applications. There are some performance
enhancements in the implementation, including data caching, parallel access to
bus masters, and aggregation of device communication. Still the fundemental
goal has been ease of use, flexibility and correctness rather than speed.
DS2890¶
The
D2890 (3) allows variable resistance under 1-wire control. Possible
uses are analog feedback mechanisms (sound pitch, light level).
Although there are provisions in the datasheet for different
DS2890
configurations (non-linear wiper ranges, multiple wipers, different resistance
scales) non are in production. To simplify implementation, this driver assumes
the standard
DS2890 design.
ADDRESSING¶
All 1-wire devices are factory assigned a unique 64-bit address. This address is
of the form:
- Family Code
- 8 bits
- Address
- 48 bits
- CRC
- 8 bits
Addressing under OWFS is in hexidecimal, of form:
- 01.123456789ABC
where
01 is an example 8-bit family code, and
12345678ABC is an
example 48 bit address.
The dot is optional, and the CRC code can included. If included, it must be
correct.
DATASHEET¶
http://pdfserv.maxim-ic.com/en/ds/DS2890.pdf
SEE ALSO¶
Programs¶
owfs (1) owhttpd (1) owftpd (1) owserver (1) owdir (1) owread (1)
owwrite (1) owpresent (1) owtap (1)
Configuration and testing¶
owfs (5) owtap (1) owmon (1)
Language bindings¶
owtcl (3) owperl (3) owcapi (3)
Clocks¶
DS1427 (3) DS1904(3) DS1994 (3) DS2404 (3) DS2404S (3) DS2415 (3) DS2417
(3)
DS2401 (3) DS2411 (3) DS1990A (3)
Memory¶
DS1982 (3) DS1985 (3) DS1986 (3) DS1991 (3) DS1992 (3) DS1993 (3) DS1995 (3)
DS1996 (3) DS2430A (3) DS2431 (3) DS2433 (3) DS2502 (3) DS2506 (3) DS28E04 (3)
DS28EC20 (3)
Switches¶
DS2405 (3) DS2406 (3) DS2408 (3) DS2409 (3) DS2413 (3) DS28EA00 (3)
Temperature¶
DS1822 (3) DS1825 (3) DS1820 (3) DS18B20 (3) DS18S20 (3) DS1920 (3) DS1921
(3) DS1821 (3) DS28EA00 (3) DS28E04 (3) EDS0064 (3) EDS0065 (3) EDS0066 (3)
EDS0067 (3) EDS0068 (3) EDS0071 (3) EDS0072 (3) MAX31826 (3)
Humidity¶
DS1922 (3) DS2438 (3) EDS0065 (3) EDS0068 (3)
Voltage¶
DS2450 (3)
Resistance¶
DS2890 (3)
Multifunction (current, voltage, temperature)¶
DS2436 (3) DS2437 (3) DS2438 (3) DS2751 (3) DS2755 (3) DS2756 (3) DS2760 (3)
DS2770 (3) DS2780 (3) DS2781 (3) DS2788 (3) DS2784 (3)
Counter¶
DS2423 (3)
LCD Screen¶
LCD (3) DS2408 (3)
Crypto¶
DS1977 (3)
Pressure¶
DS2406 (3) TAI8570 EDS0066 (3) EDS0068 (3)
Moisture¶
EEEF (3) DS2438 (3)
AVAILABILITY¶
http://www.owfs.org
AUTHOR¶
Paul Alfille (paul.alfille@gmail.com)