DS2890(3) One-Wire File System DS2890(3) NAME DS2890 - 1-Wire Digital Potentiometer SYNOPSIS Variable resistance 2C [.]XXXXXXXXXXXX[XX][/[ chargepump | wiper | address | crc8 | id | loca- tor | 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 ex- ternal 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 rela- tively 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 hexadecimal digits (0-9A- F). address starts with the family code r address is the address in reverse order, which is often used in other ap- plications 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 hexadecimal digits (0-9A-F). family read-only, ascii The 8-bit family code. Unique to each type of device. Given as upper case hexadecimal digits (0-9A-F). id 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 hexadecimal 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 asso- ciated 1-wire physical connections with a unique 1-wire code. If the con- nection is behind a Link Locator the locator will show a unique 8-byte num- ber (16 character hexadecimal) 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 set- ting (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-con- figured 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-connec- tor 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, temper- ature, 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 indi- vidually 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 principle 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 con- sistent interface. The goal is to provide an easy set of tools for a soft- ware 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 fundamental goal has been ease of use, flexibility and correct- ness 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 config- urations (non-linear wiper ranges, multiple wipers, different resistance scales) non are in production. To simplify implementation, this driver as- sumes the standard DS2890 design. ADDRESSING All 1-wire devices are factory assigned a unique 64-bit address. This ad- dress is of the form: Family Code 8 bits Address 48 bits CRC 8 bits Addressing under OWFS is in hexadecimal, 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) ID 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) Infer- noEmbedded (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 (3) EDS0066 (3) EDS0068 (3) Moisture EEEF (3) DS2438 (3) AVAILABILITY http://www.owfs.org AUTHOR Paul Alfille (paul.alfille@gmail.com) OWFS Manpage 2003 DS2890(3)
NAME | SYNOPSIS | FAMILY CODE | SPECIAL PROPERTIES | STANDARD PROPERTIES | ALARMS | DESCRIPTION | ADDRESSING | DATASHEET | SEE ALSO | AVAILABILITY | AUTHOR
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