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Dual Addressable Switch with 1kbit Memory
Hidable Dual Addressable Switch with 1kbit Memory


Dual Switch, Write-once Memory

12 [.]XXXXXXXXXXXX[XX][/[ channels | latch.[A|B|ALL|BYTE] | memory | pages/page.[0-3|ALL] | PIO.[A|B|ALL|BYTE] | power | sensed.[A|B|ALL|BYTE] | set_alarm | TAI8570/[sibling|temperature|pressure] | T8A/volt.[0-7,ALL] address | crc8 | id | locator | r_address | r_id | r_locator | type ]]

Family Code


Special Properties


read-only, unsigned integer
Is this a 1 or 2 channel switch? The DS2406 comes in two forms, one has only one PIO pin (PIO.A). Returns 1 or 2.

latch.A latch.B latch.ALL latch.BYTE

read-write, yes-no
The activity latch is set to 1 with the first negative or positive edge detected on the associated PIO channel.
Writing any data will clear latch for all (both)) channels. This is a hardware "feature" of the chip.
ALL references both channels simultaneously, comma separated
BYTE references both channels simultaneously as a single byte, with channel A in bit 0.


read-write, binary
128 bytes of non-volatile, write-once data.

pages/page.0 ... pages/page.3 pages/page.ALL

read-write, binary
Memory organized as 4 pages or 32 bytes. Memory is write-once.
ALL is the aggregate of all 4 pages, sequentially accessed.

Pio.a Pio.b Pio.all Pio.byte

read-write, yes-no
State of the open-drain output ( PIO ) pin. 0 = non-conducting (off), 1 = conducting (on) .
Writing zero will turn off the switch, non-zero will turn on the switch. Reading the PIO state will return the switch setting (flipflop in the data sheet). To determine the actual logic level at the switch, refer to the sensed property.
Note that the actual pin setting for the chip uses the opposite polarity -- 0 for conducting, 1 for non-conducting. However, to turn a connected device on (i.e. to deliver power) we use the software concept of 1 as conducting or "on".
ALL references both channels simultaneously, comma separated.
BYTE references both channels simultaneously as a single byte, with channel A in bit 0.


read-only, yes-no
Is the DS2406 powered parasitically =0 or separately on the Vcc pin =1

sensed.A sensed.B sensed.ALL sensed.BYTE

read-only, yes-no
Logic level at the PIO pin. 0 = ground. 1 = high (~2.4V - 5V ). Really makes sense only if the PIO state is set to zero (off), else will read zero.
ALL references both channels simultaneously, comma separated.
BYTE references both channels simultaneously as a single byte, with channel A in bit 0.


read-write, unsigned integer (0-331)
A number consisting of three digits XYZ, where:
channel selection
0 neither
1 A only
2 B only
3 A or B
source selection
0 undefined
1 latch
3 sensed
polarity selection
0 low
1 high

All digits will be truncated to the 0-3 (or 0-1) range. Leading zeroes are optional (and may be problematic for some shells).


  1. Responds on Conditional Search when either latch.A or latch.B (or both) are set to 1.
    Never responds to Conditional Search.


    Properties when the DS2406 (3) is built into a TAI8570.
    If the DS2406 (3) is not part of a TAI8570 or is not the controlling switch, attempts to read will result in an error.


    read-only, floating point
    Barometric pressure in millibar.


    read-only, ascii
    Hex address of the DS2406 (3) paired with this chip in a TAI8570.


    read-only, floating-point
    Ambient temperature measured by the TAI8570 in prevailing temperature units (Centigrade is the default).


    read-only, floating-point
    Uses the T8A (by Embedded Data Systems ) 8 channel voltage converter. Units in volts, 0 to 5V range. 12 bit resolution.

    Standard Properties



    read-only, ascii
    The entire 64-bit unique ID. Given as upper case hexidecimal 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 hexidecimal digits (0-9A-F).


    read-only, ascii
    The 8-bit family code. Unique to each type of device. Given as upper case hexidecimal 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 hexidecimal 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 hexidecimal) 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?


    read-only, ascii
    Part name assigned by Dallas Semi. E.g. DS2401 Alternative packaging (iButton vs chip) will not be distiguished.


    Use the set_alarm property to set the alarm triggering criteria.



    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 priciple 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 fundemental goal has been ease of use, flexibility and correctness rather than speed.


    The DS2406 (3) allows control of other devices, like LEDs and relays. It superceeds the DS2405 and DS2407 Alternative switches include the DS2408 or even DS2450
    The DS2407 is practically identical to the DS2406 except for a strange hidden mode. It is supported just like the DS2406


    The TAI-8570 Pressure Sensor is based on a 1-wire composite device by AAG Electronica. The TAI8570 uses 2 DS2406 (3) chips, paired as a reader and writer to synthesize 3-wire communication. Only 1 of the DS2406 (3) will allow temperature or pressure readings. It’s mate’s address can be shown as sibling.

    The TAI8570 uses the Intersema MS5534a pressure sensor, and stores calibration and temperature compensation values internally.

    Design and code examples are available from AAG Electronica , specific permission to use code in a GPL product was given by Mr. Aitor Arrieta of AAG and Dr. Simon Melhuish of OWW.


    All 1-wire devices are factory assigned a unique 64-bit address. This address is of the form:
    Family Code
    8 bits
    48 bits
    8 bits

    Addressing under OWFS is in hexidecimal, 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.


    See Also


    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)


    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)

    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)


    DS2423 (3)

    LCD Screen

    LCD (3) DS2408 (3)


    DS1977 (3)


    DS2406 (3) TAI8570 EDS0066 (3) EDS0068 (3)


    EEEF (3) DS2438 (3)



    Paul Alfille (

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