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

Provided by: owfs-doc_3.1p1-2ubuntu1_all

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  die  |  power  |  temphigh  |  templow   |   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.

   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.

STANDARD PROPERTIES

address
r_address
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.

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 hexidecimal digits (0-9A-F).

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

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 hexidecimal, 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

STANDARD PROPERTIES

DESCRIPTION

ADDRESSING

DATASHEET

SEE ALSO

AVAILABILITY

AUTHOR