--- name: "DS1825" section: "3" platform: "linux" package: "owfs-doc" version: "3.2p4+dfsg1-6" release: "Debian 13 (Trixie)" platforms: ["linux"] url: "https://new.carta.tech/DS1825" --- # DS1825(3) Programmable Resolution 1-Wire Digital Thermometer with ID ## NAME **DS1825** - Programmable Resolution 1-Wire Digital Thermometer with ID - **MAX31826** \- Digital Temperature Sensor with 1Kb Lockable EEPROM - **MAX31850 MAX31851** \- Cold-Junction Compensated Thermocouple ## SYNOPSIS ### Thermometer with hardware address pins (DS1825) **3B** \[.\]XXXXXXXXXXXX\[XX\]\[/\[ **fasttemp** \| **temperature** \| **temperature9** \| **temperature10** \| **temperature11** \| **temperature12** \| **latesttemp** \| **power** \| **prog\_addr** \| **temphigh** \| **templow** \| **tempres** \| **address** \| **crc8** \| **id** \| **locator** \| **r\_address** \| **r\_id** \| **r\_locator** \| **type** \]\] ### Digital Temperature Sensor with 1Kb Lockable EEPROM (MAX31826) **3B** \[.\]XXXXXXXXXXXX\[XX\]\[/\[ **temperature** \| **latesttemp** \| **power** \| **memory** \| **pages/page.\[0-15\|ALL\]** \| **prog\_addr** \| **address** \| **crc8** \| **id** \| **locator** \| **r\_address** \| **r\_id** \| **r\_locator** \| **type** \]\] ### Cold-Junction Compensated Thermocouple (MAX31850 and MAX31851) **3B** \[.\]XXXXXXXXXXXX\[XX\]\[/\[ **temperature** \| **latesttemp** \| **thermocouple** \| **fault** \| **open\_circuit** \| **ground\_short** \| **vdd\_short** \| **power** \| **prog\_addr** \| **address** \| **crc8** \| **id** \| **locator** \| **r\_address** \| **r\_id** \| **r\_locator** \| **type** \]\] ## FAMILY CODE *3B* ## SPECIAL PROPERTIES ### power *read-only,yes-no*\ Is the chip powered externally (=1) or from the parasitically from the data bus (=0)? ### prog\_addr *read-only, 0-15*\ A distiguishing feature of the **DS1825 (3)** is the ability to set hardware pins for an address (0-15). This is an alternative to the unique 64-bit *address* that is set in the factory. ### temperature *read-only, floating point*\ Measured temperature with 12 bit resolution. For the **MAX31850 MAX 31851** this is the *cold-junction temperature* -- the temperature at the chip. See *thermocouple* ### temperature9 temperature10 temperature11 temperature12 *read-only, floating point* ( **DS1825** only) Measured temperature at 9 to 12 bit resolution. There is a tradeoff of time versus accuracy in the temperature measurement. The **MAX31826 MAX31850 MAX31851** measure all temperatures at 12 bit resoltion and will return that resolution to all the possible temperature properties. ### 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* ### thermocouple *read-only, floating point* ( **MAX31850 MAX31851** only) Measured temperature of the thermocouple at 16bit resolution. Cold-junction temperature compensated. The actual thermocouple type used is set by the selected chip type, and is not discoverable in software. ## 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. The **MAX31826** does NOT have temperature thresholds and temperature alarm. ## 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. ## MEMORY Only the **MAX31826** supports memory functions. ### pages/page.0 .. pages/page.15 pages/page.ALL *read/write, binary*\ EEPROM memory pages of 8 bytes each. See the datasheet about locking contents. ### memory *read/write, binary*\ EEPROM memory of 128 bytes. See the datasheet about locking contents. ## FAULT REPORTING Only the **MAX31850 MAX31851** supports fault reporting. ### fault *read-only, yes-no*\ Fault in last thermocouple conversion ### open\_circuit *read-only, yes-no*\ Thermocouple leads disconnected. ### ground\_short *read-only, yes-no*\ Thermocouple lead shorted to ground. ### vdd\_short *read-only, yes-no*\ Thermocouple lead shorted to supply voltage. ## 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. ### DS1825 The **DS1825 (3)** is one of several available 1-wire temperature sensors. Alternatives are the **DS18S20 (3),** **DS18B20 (3),** and **DS1822 (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).** The **DS1825 (3)** can select between 4 resolutionsspanning the fastest/roughest and slowest/best. ### MAX31826 The **MAX31826** shares a family code with the **DS1825** but has differences in some of its functions. The **MAX31826** has 128 btes of EEPROM memory (as 16 pages of 8 bytes) while the **DS1825** has no memory available. The **MAX31826** measures temperature at 12 bit resolution as fast as the **DS1825's** lowest resolution (and always uses 12-bit resolution). On the other hand it has no temperature thresholds or alarm function. ## 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. Both the **MAX31826** and the **DS1825** allow hardware selection of part of the address, which can assist selecting between chips is some circuit designs. ## DATASHEET - **DS1825** http://pdfserv.maxim-ic.com/en/ds/DS1825.pdf - **MAX31826** http://datasheets.maxim-ic.com/en/ds/MAX31826.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)