Abstract
This paper presents a hardware and softwareapplication using the 1-wire technology. The application hasseveral components: 1-wire network of iButton® type devices,addressable switches, serial EEPROM memories, the softwarepackage developed for Windows operating system. Theapplication achieves several goals: 1-wire network interrogation,data processing, implementation of several control functions ofidentification and authorizing type. The solutions given haveadvantage of the hardware simplicity, which is specific to the 1-wire technology, and high efficiency in building complex networkarchitectures. The practical usefulness of the applicationpresented is to be found in the industrial field, in intelligentbuilding, in alarm and anti-burglary systems, in sensor networks,etc.
Keywords - 1-wire network, iButton®, addressable switch
I. INTRODUCTION
In the domain of identification traditional technologies areused, such as the bar codes applied on surfaces, the magneticstripes, the chip cards, and the RFID labels. To thesetechnologies can be added another successful one, which isbased on the 1-wire communication network.The 1-wire technology has emerged from the evolution ofthe semiconductor technology. It was designated to somespecific applications to substitute the identification by paperlabel based on bar codes for the electronic circuits. DallasSemiconductor was the first producer which developed a largeused automated identification through attached chips to objectsor persons.The iButtonR technology belongs to the category of thetechnologies of identification by touching. The simplestidentification method can be realized by using a microsystemwith two external electrical wire connexions: signal andground. The general advantages of iButtonR versus otherssystems are: the reading without expensive optical devices, thehundredfold increased storage of data as compared to a barcode, the identification through a unique serial number (whichcan represent a node in a global network of a practicallyunlimited dimension), the content of the iButtonR chip can bemodified while it is attached to the object, it can allow over 1milion programming cycles of EEPROM memory, it has agood adaptation to hard environments (corrosion, shocks,vibrations, etc.), reading and writing are done by means ofsmall-sized portable having a reduced energy consumption, ithas multifunctionality by integrating, into the same device,another functions (temperature and humidity sensors, etc.).
II. 1-WIRE INTERFACE
The 1-wire concept links the master initiating comunicationand the slave autosincronising with master signals. The timelogic of master and slave must measure and generate digitalpulses of diferent lengths.In the idle state, the 1-wire bus is in ”1” logical state andpresents a way of high impedance for the applied operatingsignals. Any connected device to bus must capable to pulldown 1-wire bus in the ”0” state at the desired time using anoutput of type open-colector. To stop a data transfer inprogress, the bus must to pass in idle state from which thetransaction can continues later.
A. Operating tension levels
The most 1-wire slave devices work in [2,8V – 5,25V]range. With few exceptions, the 1-wire device do not havesupply pins; they take the energy from the 1-wire bus (so call“parasitic supply”) or from an embedded battery (at someiButtonR devices). Parasitic supply uses an on-chip capacitor(≥ 800pF) and a diode serialized with a resistor for the take ofenergy from 1-wire bus when tension on bus is higher as thetension on capacitor.For a correct functioning of “parasitic energy”, someconditions specified in data sheets (VPUP, RPUP, tREC, etc.)must realized. The values of restoration time are given for anetwork with one slave. For networks with more slaves, therestoration time need to be extended, or the value of pull upresistor can be reduced [AN3829].
B. Additional energy
As a rule, “parasitic energy” assures enough energy forcommunication (addressing, reading, and writing). Moreenergy is necessary for writing in some devices, among whichiButtonR devices with EEPROM memory. This energy mustbe delivered at specified times from protocol, when 1-wire busis idle