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Table of Contents

Name

DS1821 - Programmable Digital Thermostat and Thermometer

Synopsis

Thermostat.

thermostat [/[ temperature | temphigh | templow | polarity ]]

Family Code

none

Special Properties

temperature

read-only, floating point
9-bit resolution temperature. Units are selected from the invoking command line. See owfs(1) or owhttpd(1) for choices. Default is Celsius. Conversion takes 1 second.

temphigh templow

read-write. floating point
Temperature limits for alarms. Units are selected from the invoking command line. See owfs(1) or owhttpd(1) for choices. Default is Celsius.
Note that alarms are not implemented.

Standard Properties

type

read-only, ascii
Chip type: DS1821

Alarms

None implemented.

Description

1-Wire

1-wire is a wiring protocol and series of devices designed and manufactured by Dallas Semicondictor, Inc. The bus is a low-power low-speed low-connector scheme where the data line can also provide power.

Each device is uniquely unalterably numbered during manufacture. There is a wide variety of devices, including memory, sensors (humidity, temperature, voltage, contact, current), switches, timers, loggers, and more complex devices (like thermocouple sensors) can be built wit hte basic devices. There are also 1-wire devices that have encryption included.

The 1-wire bus is accessed via one of a number of serial, parallel or USB adapters.

OWFS design

OWFS is a suite of programs that fundementally make the 1-wire bus and its devices easily accessible. The underlying priciple is to create a virtual filesystem, with the unique ID being the directory, and the individual properties of the device files.

There is optional data caching to improved performance, but possible confusion over stale data.

Ds1821

The DS1821 (3) is a unique 1-wire device. It is unaddressable, and can be put in inaccessible mode.

Addressing

Unlike all other 1-wire chips, the DS2821 (3) has no unique address. It is addressed as thermostat and will not announce itself in device discovery (directory listing).

Datasheet

http://pdfserv.maxim-ic.com/en/ds/DS1821.pdf

See Also

Programs

owfs (1) owhttpd (1) owftpd (1) owserver (1)

Language bindings

owtcl (3) owperl (3)

Clocks

DS1427 (3) DS1904(3) DS1994 (3) DS2404 (3) DS2404S (3) DS2415 (3) DS2417 (3)

ID

DS2401 (3) DS1990A (3)

Memory

DS1982 (3) DS1985 (3) DS1986 (3) DS1991 (3) DS1992 (3) DS1993 (3) DS1995 (3) DS1996 (3) DS2431 (3) DS2433 (3) DS2502 (3) DS2506 (3) DS2804 (3)

Switches

DS2405 (3) DS2406 (3) DS2408 (3) DS2409 (3) DS2413 (3)

Temperature

DS1822 (3) DS18B20 (3) DS18S20 (3) DS1920 (3) DS1921 (3) DS1821 (3)

Humidity

DS1922 (3)

Voltage

DS2450 (3)

Resistance

DS2890 (3)

Multifunction

DS2436 (3) DS2438 (3) DS2760 (3)

Counter

DS2423 (3)

LCD Screen

LCD (3) DS2408 (3)

Crypto

DS1977 (3)

Availability

http://owfs.sourceforge.net

Author

Paul Alfille (palfille@earthlink.net)


Table of Contents

© 2003-4 Paul H. Alfille and The owfs Team
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