2C [.]XXXXXXXXXXXX[XX][/[ chargepump | wiper | address | crc8 | id | locator | r_address | r_id | r_locator | type ]]
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).
wiperread-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.
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 applications and labeling.
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).
The 8-bit family code. Unique to each type of device. Given as upper case hexadecimal digits (0-9A-F).
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.
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 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?
Part name assigned by Dallas Semi. E.g. DS2401 Alternative packaging (iButton vs chip) will not be distiguished.
ALARMSThe 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.
1-Wire1-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 designOWFS 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 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.
DS2890The 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.
ADDRESSINGAll 1-wire devices are factory assigned a unique 64-bit address. This address is of the form:
- Family Code
- 8 bits
- 48 bits
- 8 bits
Addressing under OWFS is in hexadecimal, of form:
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.
Programsowfs (1) owhttpd (1) owftpd (1) owserver (1) owdir (1) owread (1) owwrite (1) owpresent (1) owtap (1)
Configuration and testingowfs (5) owtap (1) owmon (1)
Language bindingsowtcl (3) owperl (3) owcapi (3)
ClocksDS1427 (3) DS1904(3) DS1994 (3) DS2404 (3) DS2404S (3) DS2415 (3) DS2417 (3)
IDDS2401 (3) DS2411 (3) DS1990A (3)
MemoryDS1982 (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)
SwitchesDS2405 (3) DS2406 (3) DS2408 (3) DS2409 (3) DS2413 (3) DS28EA00 (3)
TemperatureDS1822 (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)
HumidityDS1922 (3) DS2438 (3) EDS0065 (3) EDS0068 (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)
LCD ScreenLCD (3) DS2408 (3)
PressureDS2406 (3) TAI8570 EDS0066 (3) EDS0068 (3)
MoistureEEEF (3) DS2438 (3)
AUTHORPaul Alfille ([email protected])