Ubuntu Manpage: DS28EA00 - 1-Wire Digital Thermometer with Sequence Detect and PIO

NAME

       DS28EA00 - 1-Wire Digital Thermometer with Sequence Detect and PIO

SYNOPSIS

       Thermometer, PIO and Chain.

       42  [.]XXXXXXXXXXXX[XX][/[  fasttemp  |  temperature  |  temperature9  |  temperature10  |
       temperature11 | temperature12 | latesttemp | die | power | temphigh | templow | tempres  |
       PIO.A|B|ALL.BYTE | latch.A|B|ALL.BYTE | sensed.A|B|ALL.BYTE

       address | crc8 | id | locator | r_address | r_id | r_locator | type ]]

FAMILY CODE

SPECIAL PROPERTIES

   power
       read-only,yes-no
       Is the chip powered externally (=1) or from the parasitically from the data bus (=0)?

TEMPERATURE PROPERTIES

   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

PIO PROPERTIES

   PIO.A|B|ALL|BYTE
       read-write, yes-no
       Two  channels  of  sensors/switches.  We  use   the   logical   raqther   than   eletrical
       interpretation: 0=off (non-conducting) 1=on (conducting -- to ground)

       The PIO channels are alternatively used for the sequence-detect (chain) mode.

       Reading sensed gives the inverse value of the cooresponding PIO.

       Reading PIO gives the actual pin values. Use the latch property to see how the pin is set.

   latch.A|B|ALL|BYTE
       read-only, yes-no
       Set (intended) va;ue of the PIO pins.

   sensed.A|B|ALL|BYTE
       read-only, yes-no
       Actual logical level at the PIO pins.

SPECIAL PROPERTIES

   power
       read-only,yes-no
       Is the chip powered externally (=1) or from the parasitically from the data bus (=0)?

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.

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

DS28EA00
The DS28EA00 (3) is one of several available 1-wire temperature sensors. It is the
replacement for the DS18S20 (3) Alternatives are DS1822 (3) as well as temperature/vlotage
measurements in the DS2436 (3) and DS2438 (3). For truly versatile temperature
measurements, see the protean DS1921 (3) Thermachron (3).
The DS28EA00 has special switch/sequence detect properties. In sequence mode, the PIO pins
are daisy-chained to the next DS28EA00, allowing the system to step through the physical
sequence of the DS28EA00s.

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/DS28EA00.pdf

AVAILABILITY

       http://www.owfs.org

AUTHOR

       Paul Alfille (paul.alfille@gmail.com)

NAME

SYNOPSIS

FAMILY CODE

SPECIAL PROPERTIES

TEMPERATURE PROPERTIES

PIO PROPERTIES

SPECIAL PROPERTIES

TEMPERATURE ALARM LIMITS

TEMPERATURE RESOLUTION DEFAULT VALUE

STANDARD PROPERTIES

DESCRIPTION

ADDRESSING

DATASHEET

SEE ALSO

AVAILABILITY

AUTHOR