| DS1822(3) | One-Wire File System | DS1822(3) |
DS1822 - Econo 1-Wire Digital Thermometer
Thermometer.
22 [.]XXXXXXXXXXXX[XX][/[ fasttemp | temperature | temperature9 | temperature10 | temperature11 | temperature12 | latesttemp | die | power | temphigh | templow | tempres | trim | trimblanket | trimvalid | address | crc8 | id | locator | r_address | r_id | r_locator | type ]]
22
read-only,yes-no
Is the chip powered externally (=1) or from the parasitically from the data
bus (=0)?
read-only, floating point
Measured temperature with 12 bit resolution.
read-only, floating point
Measured temperature at 9 to 12 bit resolution. There is a tradeoff of time
versus accuracy in the temperature measurement.
read-only, floating point
Measured temperature at 9 to 12 bit resolution, depending on the resolution of
the latest conversion on this chip. Reading this node will never trigger a
temperature conversion. Intended for use in conjunction with
/simultaneous/temperature.
read-only, floating point
Equivalent to temperature9
When the device exceeds either temphigh or templow temperature threshold the device is in the alarm state, and will appear in the alarm directory. This provides an easy way to poll for temperatures that are unsafe, especially if simultaneous temperature conversion is done.
Units for the temperature alarms are in the same temperature scale that was set for temperature measurements.
Temperature thresholds are stored in non-volatile memory and persist until changed, even if power is lost.
read-write, integer
Shows or sets the lower limit for the high temperature alarm state.
read-write, integer
Shows or sets the upper limit for the low temperature alarm state.
read-write, integer
The device employs a non-volatile memory to store the default temperature
resolution (9, 10, 11 or 12 bits) to be applied after power-up. This is
useful if you use simultaneous temperature conversions. Reading this
node gives you the value stored in the non-volatile memory. Writing sets a
new power-on resolution value.
As a side effect, reading this node resets the temperature resolution used by simultaneous temperature conversions to its power-on value. It also affects the resolution value used by latesttemp, to scale the latest conversion value, so make sure to re-sample the temperature before accessing latesttemp after writing or reading the tempres value.
There are a group of obscure internal properties exposed to protect against an hardware defect in certain batches of the B7 die of some DS18x20 chips. See http://www.1wire.org/en-us/pg_18.html or request AN247.pdf from Dallas directly.
read-only,ascii
Two character manufacturing die lot. "B6" "B7" or
"C2"
read-write,unsigned integer
32 bit trim value in the EEPROM of the chip. When written, it does not seem to
read back. Used for a production problem in the B7 die.
Read allowed for all chips. Only the B7 chips can be written.
read-write,yes-no
Writing non-zero (=1) puts a default trim value in the chip. Only applied to
the B7 die. Reading will be true (non-zero) if trim value is the
blanket value. Again, only B7 chips will register true, and since the
written trim values cannot be read, this value may have little utility.
read-only,yes-no
Is the trim value in the valid range? Non-zero if true, which includes
all non-B7 chips.
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 applications and labeling.
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).
read-only, ascii
The 8-bit family code. Unique to each type of device. Given as upper
case hexadecimal digits (0-9A-F).
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.
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 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.
read-only, yes-no
Is the device currently present on the 1-wire bus?
read-only, ascii
Part name assigned by Dallas Semi. E.g. DS2401 Alternative packaging
(iButton vs chip) will not be distiguished.
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 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 fundamental goal has been ease of use, flexibility and correctness rather than speed.
The DS1822 (3) is one of several available 1-wire temperature sensors. Alternatives are the DS18S20 (3), DS18B20 (3) as well as temperature/voltage measurements in the DS2436 (3) and DS2438 (3). For truly versatile temperature measurements, see the protean DS1921 (3) Thermachron (3).
Although the DS1822 (3) can select between 4 resolutions, this program simplifies the interface by only implementing the fastest/roughest and slowest/best.
All 1-wire devices are factory assigned a unique 64-bit address. This address is of the form:
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.
http://pdfserv.maxim-ic.com/en/ds/DS1822.pdf
owfs (1) owhttpd (1) owftpd (1) owserver (1) owdir (1) owread (1) owwrite (1) owpresent (1) owtap (1)
owfs (5) owtap (1) owmon (1)
owtcl (3) owperl (3) owcapi (3)
DS1427 (3) DS1904 (3) DS1994 (3) DS2404 (3) DS2404S (3) DS2415 (3) DS2417 (3)
DS2401 (3) DS2411 (3) DS1990A (3)
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)
DS2405 (3) DS2406 (3) DS2408 (3) DS2409 (3) DS2413 (3) DS28EA00 (3)
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)
DS1922 (3) DS2438 (3) EDS0065 (3) EDS0068 (3)
DS2450 (3)
DS2890 (3)
DS2436 (3) DS2437 (3) DS2438 (3) DS2751 (3) DS2755 (3) DS2756 (3) DS2760 (3) DS2770 (3) DS2780 (3) DS2781 (3) DS2788 (3) DS2784 (3)
DS2423 (3)
LCD (3) DS2408 (3)
DS1977 (3)
DS2406 (3) TAI8570 (3) EDS0066 (3) EDS0068 (3)
EEEF (3) DS2438 (3)
http://www.owfs.org
Paul Alfille (paul.alfille@gmail.com)
| 2003 | OWFS Manpage |