--- name: "DS2438" section: "3" platform: "linux" package: "owfs-doc" version: "3.2p4+dfsg1-6" release: "Debian 13 (Trixie)" platforms: ["linux"] url: "https://new.carta.tech/DS2438" --- # DS2438(3) Smart Battery Monitor ## NAME **DS2438** - Smart Battery Monitor ## SYNOPSIS ### Temperature Voltages and Current. **26** \[.\]XXXXXXXXXXXX\[XX\]\[/\[ **CA** \| **EE** \| **date** \| **disconnect/date** \| **disconnect/udate** \| **endcharge/date** \| **endcharge/udate** \| **IAD** \| **offset** \| **pages/page.\[0-7\|ALL\]** \| **temperature** \| **latesttemp** \| **udate** \| **VAD** \| **VDD** \| **vis** \| **address** \| **crc8** \| **id** \| **locator** \| **r\_address** \| **r\_id** \| **r\_locator** \| **type** \]\] ### Humidity sensor **26** \[.\]XXXXXXXXXXXX\[XX\]\[/\[ **HIH4000/humidity** \| **HIH5030/humidity** \| **HTM1735/humidity** \| **DATANAB/reset** \| **DATANAB/humidity** \| **humidity** \| **temperature** \]\] ### Barometer **26** \[.\]XXXXXXXXXXXX\[XX\]\[/\[ **B1-R1-A/pressure** \| **B1-R1-A/gain** \| **B1-R1-A/offset** \| \]\] ### Light **26** \[.\]XXXXXXXXXXXX\[XX\]\[/\[ **S3-R1-A/current** \| **S3-R1-A/illuminance** \| **S3-R1-A/gain** \]\] ## FAMILY CODE *26* ## SPECIAL PROPERTIES ### pages/page.0 ... pages/page.7 pages/page.ALL *read-write, binary*\ Memory is split into 8 pages of 8 bytes each. Only the pages 3-7 are really available, and some of that appears to be reserved. See the datasheet for details.\ *ALL* is an aggregate of the pages. Each page is accessed sequentially. ### temperature *read-only, floating point*\ *Temperature* read by the chip at high resolution (~13 bits). Units are selected from the invoking command line. See **[owfs(1)](/owfs/1.md)** or **[owhttpd(1)](/owhttpd/1.md)** for choices. Default is Celsius. Conversion takes ~20 msec. ### latesttemp *read-only, floating point*\ Latest measured temperature. Reading this node will never trigger a temperature conversion. Intended for use in conjunction with **/simultaneous/temperature.** ### VAD VDD *read-only, floating point*\ Voltage read (~10 bits) at the one of the chip's two supply voltages. Range VDD= 2.4V to 10V, VAD=1.5 to 10V. ### vis *read-only, floating point*\ Current sensor reading, as a voltage difference. Value is in volts.\ Actual current depends on Rsens resistor (see datasheet).\ The formula for current is I = vis / Rsens\ with units in Amps and Ohms.\ Current measurement will be temporarily enabled (see *Ienable* ) if not currently enabled (pun intended) for this reading. ## CONFIGURATION PROPERTIES ### CA *read-write, yes-no*\ *Current Accumulator Configuration* flag bit. If "on" (1) current is stored in page 7 bytes 4-7. If "off" (0) that page can be used for general storage. See the datasheet for more information. ### EE *read-write, yes-no*\ *Current Accumulator Shadow* flag bit. If "on" (1) current reading is stored to EEPROM. If "off" (0) that data will be lost when chip loses power. See the datasheet for more information ### IAD *read-write, yes-no*\ *Current A/D Control* flag bit. If "on" (1) current measured at 36.41 Hz. If "off" (0) current measurements won't be made. See the datasheet for more information. ## DATE PROPERTIES ### date *read-write, ascii*\ 26 character date representation of the *counter* value. Increments once per second.\ Setting *date* to a null string will put the current system time.\ Accepted date formats are:\ \ Sat\[urday\] March 12 12:23:59 2001\ \ Apr\[il\] 4 9:34:56 2002\ \ 3/23/04 23:34:57\ \ current locale setting (your system's format) ### disconnect/date *read-write, ascii*\ 26 character date representation of the *disconnect/udate* value. Time when the battery pack waws removed from the charger. Format is the same as the *date* property. ### disconnect/udate *read-write, unsigned integer*\ Representation of *disconnect/date* as a number. See *udate* for details. ### endcharge/date *read-write, ascii*\ 26 character date representation of the *endcharge/udate* value. Format is the same as the *date* property. ### endcharge/udate *read-write, unsigned integer*\ Representation of *endcharge/date* as a number. See *udate* for details. ### udate *read-write, unsigned integer*\ Time represented as a number. *udate* increments once per second.\ Usually set to unix time standard: number of seconds since Jan 1, 1970. The *date* field will be the unix representation (ascii text) of *udate* and setting either will change the other. ## HUMIDITY PROPERTIES ### HIH4000/humidity *read-only, floating point*\ Relative humidity, as percent (1-100 scale).\ This value is for a design based on Honeywell's HIH-4000 humidity sensor. ### HIH5030/humidity *read-only, floating point*\ Relative humidity, as percent (1-100 scale).\ This value is for a design based on Honeywell's HIH-5030/5031 humidity sensor. ### HTM1735/humidity *read-only, floating point*\ Relative humidity, as percent (1-100 scale).\ This value is for a design based on Humirel's HTM-1735 humidity sensor. ### DATANAB/humidity *read-only, floating point*\ Based on DataNAB's humidity sensor. It uses a HIH-4000 sensor and the current sensning rather than voltage readings from the DS2438. Calibration values are stored on chip, and a check field is stored in chip memory. ### DATANAB/reset *write-only, yes-no*\ Used to read calibration values and set the chip to current reading more. Should be automatically called when a humidity reading is requested. ### humidity *read-only, floating point*\ Relative humidity, as percent (1-100 scale).\ The **DS2438** actually does not read humidity, but a widely available and publicised circuit based on the chip, does. This design is for the common Honeywell HIH-3610 humidity chip. The mostly compatible HIH-4000 chip uses different temperature compensation, so is better read from the *HIH4000/humidity* value. See the datasheets for details.\ If the chip is instead a DATANAB design, the *DATANAB/humidity* value will be automatically used. ## BAROMETER PROPERTIES ### B1-R1-A/pressure *read-only, floating point*\ Pressure reading, as milli-bars, or other unit depending on *settings/units/pressure\_scale*.\ This value is for the B1-R1-A barometer from Hobby-Boards, and assumes the standard calibration. ### B1-R1-A/gain *read/write, floating point*\ Calibration of pressure gain, as signed number, expressed as the same units as *B1-R1-A/pressure* per volt.\ This value will be multiplied with the measured voltage to get the *B1-R1-A/pressure* reading. It may have to be fine tuned for calibration purposes, although with the standard sensor, it will often be good enough to keep it as is. ### B1-R1-A/offset *read/write, floating point*\ Calibration of pressure offset, as signed number, same units as *B1-R1-A/pressure.*\ This value will be added to the *B1-R1-A/pressure* reading. The default value is 904.7 millibars, which may be altered to to compensate for elevation. ## SOLAR SENSOR PROPERTIES ### S3-R1-A/current *read-only, floating point*\ Photo-diode current, in micro-amperes.\ This value is for the S3-R1-A solar radiation sensor from Hobby-Boards. Due to noise and offsets, this value may read as a negative number in low light conditions. The *offset* register can be modified to reduce the offset as much as possible. ### S3-R1-A/illumination *read-only, floating point*\ Illumination, in lux. Always a positive number.\ This value is the lux reading from the solar sensor, taking *S3-R1-A/gain into consideration.* ### S3-R1-A/gain *read/write, floating point*\ Calibration of photo-diode gain expressed as lux per micro-amperes. The default value is for the SFH203P photo-diode from Osram, used bare. A different gain may be used for instance to compensate for an integrathing, white sphere placed over the diode.\ This value is for the S3-R1-A solar radiation sensor from Hobby-Boards, using the SFH203P photo-diode from Osram. ## MULTISENSOR PROPERTIES ### MultiSensor/type *read-only, ascii*\ For *iButtonLink's MultiSensor* line of 1-wire devices, give the specific configuration based on a data byte set in memory. (Byte 0 of page 3). This can help interpretation of the sensor values, distinguishing, current from water from light. ### offset *read-write, integer*\ Correction for *current* readings. A value between -256 and 255. See the datasheet for details. Should be set to the negative of a true zero *current* reading. ## 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. ## ALARMS None. ## 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. ### DS2438 The **DS2438 (3)** is a more complete form of the **DS2436** battery chip. Current sensing is available, but not implemented. The major advantage compared to the **DS2436** is that two voltages can be read, allowing one to correct circuit measurements for supply voltage and temperature. A better comparison is the **DS276x** family of chips. ## 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/DS2438.pdf\ http://pdfserv.maxim-ic.com/en/an/humsensor.pdf\ http://goo.gl/o9DH0 (Redirects to 009012\_2.pdf PDF file on honeywell.com website)\ http://www.phanderson.com/hih-4000.pdf\ http://www.humirel.com/product/fichier/HTM1735%20RevG%20.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) Egil Kvaleberg