IRDC, Part 1: Physical Layer Infrared Data …

1 Number: 82513 Rev. , 20-Sep-06 IRDC, part 1: Physical LayerVishay SemiconductorsInfrared data communication according to IrDA StandardPart 1: Physical LayerWhat is IrDA? IrDA is the abbreviation for the Infrared data Associ-ation, a non-profit organization for setting standardsin IR serial computer connections. The following is anoriginal excerpt from the IrDA Web site ( ).Executive SummaryIrDA was established in 1993 to set and support hard-ware and software standards which create infraredcommunications links. The Association's charter is tocreate an interoperable, low-cost, low-power, half-duplex, serial data interconnection standard that sup-ports a walk-up, point-to-point user model that isadaptable to a wide range of applications anddevices.

2 IrDA standards support a broad range ofcomputing, communications, and consumer in scope, IrDA is a non-profit corporationheadquartered in Walnut Creek, California, and led bya Board of Directors which represents voting mem-bership worldwide. As a leading high technology stan-dards association, IrDA is committed to developingand promoting Infrared standards for the hardware,software, systems, components, peripherals, commu-nications, and consumer markets. Industry OverviewInfrared (IR) communications is based on technologywhich is similar to the remote control devices such asTV and entertainment remote controls used in mosthomes today.

3 IR offers a convenient, inexpensive andreliable way to connect computer and peripheraldevices without the use of cables. IrDA connectivity isbeing incorporated into most notebook PCs to bringthe most cost-effective and easy to use support avail-able for wireless are few US, European or other internationalregulatory can ship IrDA-enabled products glo-bally without any constraints, and IrDA functionaldevices can be used by international travellers wher-ever they are, and interference problems are for IR communications have been devel-oped by IrDA. In September 1993, IrDA determinedthe basis for the IrDA SIR data Link Standards.

4 InJune 1994, IrDA published the IrDA standards whichincludes Serial Infrared (SIR) Link specification, LinkAccess Protocol (IrLAP) specification, and Link Man-agement Protocol (IrLMP) specification. IrDAreleased extensions to SIR standard including4 Mbit/s in October 1995. The IrDA Standard Specifi-cation has been expanded to include high speedextensions of Mbit/s and Mbit/s. This exten-sion will require an add-in card to retrofit existing PCswith high speed IR, and a synchronous communica-tions controller or 1995, several market leaders announced orreleased products with IR features based on IrDAstandards. These products include components,adapters, printers, PCs, PDAs, notebook computers,LAN access, and software applications.

5 In November1995, the Microsoft Corporation announced it hadadded support for IrDA connectivity to the MicrosoftWindows 95 operating system, enabling low-costwireless connectivity between Windows 95 basedPCs and peripheral devices. IrDA's interoperable Infrared serial data link featureslow power consumption with data speeds up to 4 Mbit/s, allowing a cordless 'walk-up-to' data transferin a simple, yet compelling way. Applications are inboth consumer and commercial markets with a uni-versal data connection relevant in the use of dockingand input units, printers, telephones, desktop/ laptopPCs, network nodes, ATMs, and handheld mobilepeers (PDA meets PDA).

6 Yesterday s systems withIR capabilities such as Newton, Omnibook, Wizardand Zoomer are not easily compatible with each otheror other complementary devices. IrDA is the responsein which many segments of the industry have commit-ted themselves to realizing the opportunity of a gen-eral standard providing data links which are non-interfering and interoperable. The IrDA - StandardThe current IrDA Physical Layer standard is and includes all changes and add-ons up to VFIR with 16 Mbit/s. Version replaced version whichis obsolete as are all former versions from to to these versions currently can describeonly historical steps of the IrDA - , part 1: Physical LayerDocument number: 82513 Rev.

7 , 20-Sep-06 vishay IrDA Transmission WorksThe transmission in an IrDA-compatible mode (some-times called SIR for serial IR) uses, in the simplestcase, the RS232 port, a built-in standard of all com-patible PCs. With a simple interface, shortening thebit length to a maximum of 3/16 of its original lengthfor power-saving requirements, an Infrared emittingdiode is driven to transmit an optical signal to type of transmission covers the data range up kbit/s which is the maximum data rate sup-ported by standard UARTs (see figure 1). The mini-mum demand for transmission speed for IrDA is only9600 bit/s. All transmissions must be started at thisfrequency to enable compatibility.

8 Higher speeds area matter of negotiation of the ports after establishingthe speeds require special interfaces which oper-ate at Mbit/s and use a similar pulse-shorteningprocess as in the RS232-related mode, but with apulse reduction to 1/4 of the original pulse length. Thefastest data rate supported by IrDA is Mbit/s (oftencalled FIR), operating with 125-ns pulses in a 4-PPM(PPM = Pulse-PositionModulation) mode. The typicalinterfaces for the various modes are shown in figure2. In the following chapter "IrDA Standard - PhysicalLayer", the definitions of the IrDA standard are given. Optical output power and receiver sensitivity are setto a level where a point-and-shoot activity (r 15q) issufficient for point-to-point communication , but pre-vents the pollution of the ambient by straying need-less power.

9 Transmission over a distance of at least1 m is ensured. The detector front end receives thetransmitted signal, re-shapes the signal and feeds itto the port. The system works in a half-duplex modethat allows only one transmission direction to beactive at any given frequencies up to kbit/s, the minimum out-put intensity is defined with 40 mW/sr. For higherspeeds, a higher output intensity of 100 W/sr mini-mum is used. The sensitivity thresholds are40 mW/m2 and 100 mW/m2 for SIR and FIR wavelength chosen for the standard is between850 nm and 900 additional IrDA standard was generated in 1997(voted Feb. 1998) for Control applications, the so-called IrControl standard.

10 This standard is using the IEC1603-1 sub carrier fre-quency allocation with a carrier at 1500 kHz. Thetransmission capacity is 72 kbit/s. This system hasstill some compatibility problems with the SIR/FIRIrDA Standard. One of the disadvantages is that thedetector circuitry is different from the other, base-band system. Therefore, integrating both into oneapplication is expensive. Using IrControl and SIR/FIRin one application would imply that two IR hardwarechannels must be built-in. The Very Fast IR (VFIR,min. 16 Mbit/s transfer rate over more than 1 m)established in 1999. What do I need to enable IrDA Transmission?The simplest way of optical interfacing in the SIRmode is shown in figure 1.