--- name: "DS1822" section: "3" platform: "linux" package: "owfs-doc" version: "3.2p4+dfsg1-6" release: "Debian 13 (Trixie)" platforms: ["linux"] url: "https://new.carta.tech/DS1822" --- # DS1822(3) Econo 1-Wire Digital Thermometer ## NAME **DS1822** - Econo 1-Wire Digital Thermometer ## SYNOPSIS Thermometer. **22** \[.\]XXXXXXXXXXXX\[XX\]\[/\[ **fasttemp** \| **temperature** \| **temperature9** \| **temperature10** \| **temperature11** \| **temperature12** \| **latesttemp** \| **die** \| **power** \| **temphigh** \| **templow** \| **tempres** \| **trim** \| **trimblanket** \| **trimvalid** \| **address** \| **crc8** \| **id** \| **locator** \| **r\_address** \| **r\_id** \| **r\_locator** \| **type** \]\] ## FAMILY CODE *22* ## SPECIAL PROPERTIES ### power *read-only,yes-no*\ Is the chip powered externally (=1) or from the parasitically from the data bus (=0)? ### temperature *read-only, floating point*\ Measured temperature with 12 bit resolution. ### temperature9 temperature10 temperature11 temperature12 *read-only, floating point*\ Measured temperature at 9 to 12 bit resolution. There is a tradeoff of time versus accuracy in the temperature measurement. ### latesttemp *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.** ### fasttemp *read-only, floating point*\ Equivalent to *temperature9* ## TEMPERATURE ALARM LIMITS 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. ### temphigh *read-write, integer*\ Shows or sets the lower limit for the high temperature alarm state. ### templow *read-write, integer*\ Shows or sets the upper limit for the low temperature alarm state. ## TEMPERATURE RESOLUTION DEFAULT VALUE ### tempres *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. ## TEMPERATURE ERRATA 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. ### errata/die *read-only,ascii*\ Two character manufacturing die lot. "B6" "B7" or "C2" ### errata/trim *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. ### errata/trimblanket *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. ### errata/trimvalid *read-only,yes-no*\ Is the *trim* value in the valid range? Non-zero if true, which includes all non-B7 chips. ## 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 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 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 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? ### type *read-only, ascii*\ Part name assigned by Dallas Semi. E.g. *DS2401* Alternative packaging (iButton vs chip) will not be distiguished. ## 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 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. ### DS1822 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. ## 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 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/DS1822.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) InfernoEmbedded (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)