Irda Whitepaper

IRDA WHITE PAPER

HCL Infosystems Limited

Contents IRDA Executive Summary................................................... 3 Major Specification... ................................................. 3 Benefits of Infrared ...................... ............................ 3 Basic IRDA Usage Model......... ................ ................. 3 IRDA Implementation in Computer Systems................ 4 IRDA Devices............. ............ ............ ............... 4 IRDA Limitation............. ............ ............ ............... 4 IRDA Technology Explained............. .................................. 5 Introduction ...................................................................5 Infrared Basics ..................................... ........................5 Infrared in Consumer electronics ..................................6 The IrDA standard ..................................... ...................6 IrDA-Data Architecture and Protocol Stack - Overview .7 IrDA-Data Architecture and Protocol Stack - In detail ...8 Infrared Q & A .................................... ............ ........................11 Reference ...............................… ... ........... ........................….12

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IRDA – Executive Summary IRDA is a cordless data connection using infrared light. It is a low-cost transceiver signaling technology for two way data exchange. It provides high-speed digital exchange through the typical PC UART/serial port at 9600-115200 bits/s, and in some unit’s compatible high-speed extensions up to 1Mb/s and 4Mb/s speeds. The initials IrDA stand for the Infrared Data Association. IrDA is a nonprofit trade association with a membership of over 160 companies representing computer and telecommunications hardware, software, components and adapters

Major Specification • • • • • • •

Uses IR with peak wavelength of 0.85 to 0.90 micro-meter The transmitter's minimum and maximum intensity is 40 and 500 mW/Sr 30 degree cone transmitting area The link length is 20cm to 1 m with an error rate of less than 1 in 10**8 bits Data transfer speed 115Kbps (SIR - Serial IrDA) and 4.0 Mbps (FIR - Fast IrDA). Future development extends upto 16.0Mbps Windows 98, Windows 2000 and above API programming support Linux support started appear in open source

Benefits of Infrared • • • • • •

A worldwide standard for wireless connectivity Easy to implement and simple to use Safe in any environment No electromagnetic noise No government regulatory issues Minimum crosstalk

Basic IRDA usage model • • •

In the basic IrDA-Data usage model, there are two devices: the primary (master) and the secondary (slave). The primary device’s job is to select a device within its visual space, establish a connection, and maintain the virtual connection. The role of the secondary is to only respond when spoken to.

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HCL Infosystems Limited IR S e c o n d a r y

P ri m a r y

Figure 1 – IRDA usage model

IrDA implementation in Computer systems There are two types of IrDA based on connections, • • •

External Infrared Adapter: Interfacing through serial port and USB. Internal Infrared Adapter: This is a header (5 pins), which will be present in the motherboard itself. It has to connect an IrDA PCB module with cable to this header to make it work. The internal IRDA implementation shares one serial port in the motherboard. So when IRDA is used, the shared serial cannot be used. The selection is normally through a setting in the motherboard CMOS setting.

Figure 2 - IRDA Motherboard connector (Internal)

Figure 3 - External IRDA

IrDA Devices • • • • • • • • •

Notebooks and Handheld computers PDA’s and Palm devices Printers Scanners Mobile phones & pagers Digital Cameras Medical and Industrial equipments LAN access devices Point-Of-Sales systems

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IrDA Limitation • •

Point to point and signal can be easily blocked Limited transmission length compared to other wireless technologies

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IRDA – Technology Explained Introduction: Portable computing has become synonymous with the rapidly changing world of technology in today's work environment. Every company recognizes that in order to compete they must keep pace, as well as deploy and manage this new technology in order to maintain their competitive edge. New economic trends in the global economy will continue to push companies to find new ways to enhance productivity and maintain flexibility among their employees. In fact, portable computing according to recent studies is poised for some very dramatic growth. A trend that is likely to continue as companies deploy their workforce to a more "mobile office concept". One obstacle to achieving the goal of mobile connectivity has always been the limitation of the cable connection. Whether you are connecting to the printer, your network or exchanging data with the desktop, the cable connection is viewed as a hindrance to the effective and efficient use of the portable computer.

Infrared Basics The portion of the invisible electromagnetic spectrum consisting of radiation with wavelengths in the range 750 nm () to 1 mm (), between light and radio waves.

Radio Microwave Infrared Optical UV X-ray Gamma-ray

Wavelength (m) > 1 x 10-1 1 x 10-3 - 1 x 10-1 7 x 10-7 - 1 x 10-3 4 x 10-7 - 7 x 10-7 1 x 10-8 - 4 x 10-7 1 x 10-11 - 1 x 10-8 < 1 x 10-11

Frequency (Hz) < 3 x 109 3 x 109 - 3 x 1011 3 x 1011 - 4 x 1014 4 x 1014 - 7.5 x 1014 7.5 x 1014 - 3 x 1016 3 x 1016 - 3 x 1019 > 3 x 1019

Energy (J) < 2 x 10-24 2 x 10-24- 2 x 10-22 2 x 10-22 - 3 x 10-19 3 x 10-19 - 5 x 10-19 5 x 10-19 - 2 x 10-17 2 x 10-17 - 2 x 10-14 > 2 x 10-14

Table 1 – Electromagnetic Spectrum

Infrared or "Below Red" was discovered in the early 1800's by Sir William Hershel. He discovered upon moving a thermometer across the spectrum of colors that the heat would increase towards red. As he continued to move the thermometer passed the red the heating continue to rise. This area is what we call Infrared or also known as just beyond red.

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Infrared in Consumer electronics Consumer electronics industries started using the Infrared light as way to control their appliances for increased user friendliness in actual user environment by providing mobility / remote access / ease of use. With most pieces of consumer electronics, from camcorders to stereo equipment, an infrared remote control is usually always included. Video and audio apparatus and also lighting installations nowadays often operate on infra-red remote control. The carrier frequency of such infrared signals is typically in the order of around 36 kHz. The control codes are sent in serial format modulated to that 36 kHz carrier frequency (usually by turning the carrier on and off). There are many different coding systems in use, and generally different manufacturers use different codes and different data rates for transmission.

The IrDA standard Taking cue from consumer electronics, the IT industries also started showing interest in Infrared. In an effort to achieve a wireless connection to a full range of peripheral devices without the hassle of cable, infrared technology was born. In 1993 leaders from both the communication and computer industry formed the Infra-red Data Association (IrDA) with the sole purpose of creating a standard for infrared wireless data transfer. Figure 4 – IRDA logo

Now the IrDA association has over 120 members worldwide. It includes some of the most recognized companies in the world, such as: Apple, AT&T, ACTiSYS, Canon, Compaq, Hitachi, Intel, Hewlett Packard, Microsoft, Motorola NTT, Sony, Toshiba and many others. The specification versions are • • • •

IRDA (Infrared Data Association) Serial Infrared Physical Layer Specification Version 1.4 May 30th, 2001 IrDA (Infrared Data Association) Serial Infrared Link Access Protocol (IrLAP), Version 1.1, June 16, 1996. IrDA (Infrared Data Association) Serial Infrared Link Management Protocol, IrLMP), Version 1.1, January 23, 1996. IrDA (Infrared Data Association) Serial Infrared Physical Layer Measurement Guidelines, Version 1.0, January 16, 1998.

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IrDA (Infrared Data Association) IrMC Specification, Version 1.0.1, January 10, 1998.

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IrDA-Data Architecture and Protocol Stack Overview Communications protocols deal with many issues, and so are generally broken into layers, each of which deals with a manageable set of responsibilities and supplies needed capabilities to the layers above and below. When you place the layers on top of each other, you get what is called a protocol stack, rather like a stack of pancakes or a stack of plates. An IrDA protocol stack is the layered set of protocols particularly aimed at point-to-point infrared communications and the applications needed in that environment. Below is a picture of the IrDA protocol layers. This layering will serve as the overall structure for much of the remaining discussion.

Figure 5 – IRDA Protocol stack

The layers within this stack can be divided into two groups—required and optional protocols. Required IrDA Protocols • • • •

Physical Layer - defines data rates, handles encoding of data and framing for various speeds IrLAP - establishes the basic reliable connection by providing addressing, error detection, and retransmission capabilities IrLMP is divided into two sublayers, LM-MUX and LM-IAS. IAS - provides a directory of services on a device

Optional Protocols •

TinyTP: Tiny Transport Protocol. Adds per-channel flow control to keep things moving smoothly. This is a very important function and is required in many cases.

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IrOBEX: The Object Exchange protocol. Easy transfer of files and other data objects IrCOMM: Serial and Parallel Port emulation, enabling existing apps that use serial and parallel communications to use IR without change.

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IrDA-Data Architecture and Protocol Stack – In detail Physical Layer The IrDA Physical Layer Specification sets a standard for the IR transceiver, the modulation or encoding/ decoding method, as well as other physical parameters. IrDA uses IR with peak wavelength of 0.85 to 0.90 micro-meter. The transmitter's minimum and maximum intensity is 40 and 500 mW/Sr within a 30-degree cone. The receiver's minimum and maximum sensitivity is 0.0040 and 500 mW/(cm.cm) within a similar 30degree cone. The link length is 0 to 1 m with an error rate of less than 1 in 10**8 bits. There are three different modulation or encoding/decoding methods. The first one is mandatory for both IrDA-1.0 and IrDA- 1.1. The other two are optional and are for IrDA-1.1 only. For transfer rate of 9.6k, 19.2k, 38.4k, 57.6k or 115.2 kbps operations, a start (0) bit and a stop (1) bit is added before and after each byte of data. This is the same format as used in a traditional UART. However, instead of NRZ, a method similar to RZ is used, where a 0 is encoded as a single pulse of 1.6 micro-sec to 3/16 of a bit cell, and a 1 is encoded as the absence of such a pulse. In order to have unique byte patterns to mark beginning and ending of a frame and yet allow any binary data bytes, byte stuffing (escape sequence) is used in the body of the frame. A 16-bit CRC is used for error detection. The 9.6 kbps operation is mandatory for both IrDA-1.0 and IrDA-1.1. 19.2k, 38.4k, 57.6k and 115.2 kbps are all optional for IrDA-1.0 and IrDA-1.1. For transfer rate of 0.576M or 1.152 Mbps operation, no start or stop bits are used and the same synchronous format as HDLC is used. Again, a 0 is encoded as a single pulse (1/4 the bit cell) whereas a 1 is encoded as the absence of such a pulse. In order to ensure clock recovery, bit stuffing is used (same as in HDLC). The same 16-bit CRC is also used. Both 0.576M and 1.152 Mbps operations are optional for IrDA1.1. For transfer rate of 4.0 Mbps operation, a 4-PPM method is used. Again, no start or stop bits are used. In addition, bit/byte stuffing are not needed either. A 32- bit CRC is used in this case. This rate is used in IrDA-1.1 only. IrLAP Layer The IrDA Link Access Protocol (IrLAP) establishes the IR media access rules and various procedures for discovery, negotiation, information exchange, etc. IrLAP is a mandatory layer of the IrDA standard but not all the features are mandatory. The minimum requirements are clearly spelled out in the specification. The main media access rules are that for any station which is currently not participating in a connection, it must listen for more than 500 msec to make sure that there is no IR traffic before it starts to transmit, and that for any station which is currently participating in a connection, it must transmit a frame within any given 500 msec. Media access among the stations participating in a connection is controlled by a token-like Poll/Final bit in each frame. Transmission of user data without first establishing a connection is allowed in IrLAP. As far 11

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HCL Infosystems Limited as IrLAP is concerned, connection-less transmissions are broadcast in nature and are not acknowledged by the receiver. The discovery procedure defines an orderly way to exchange IDs. The initiator broadcasts its own ID repeatedly for a known number of times and listens between these repeated transmissions (slots). The responders randomly choose one of the slots and send their own IDs. If there is a collision, this procedure can be repeated. The negotiation procedure is used to establish a connection with operating parameters that both parties can support. Some or these parameters, such as bit rate, must be identical for both side, thus the "largest common denominator" is used. Some other parameters, such as maximum data size, are the limits of one party, which the other party must respect. After all these operating parameters are known to both parties, a connection can be established. Before this happens, all traffic (connection-less transmission of data, discovery procedure, negotiation procedure, etc.) is carried out at 9.6 kbps async. mode with maximum data size of 64 bytes. Once connection is made, the negotiated data rate can be as high as 115.2 kbps (IrDA-1.0) or 4 Mbps (IrDA-1.1), the negotiated maximum data size can be as big as 2048 bytes. During connection, the information exchange procedures are used. Frames containing user data are sequence checked in addition to CRC. There are also supervisory frames used for flow control, error recovery, and to pass the token. Connection may be one-to-one or one-to-many. One of the stations in a connection plays the role of a primary; all others play the roles of secondaries. Usually, the station that initiated the connection, or the common one in a one-to-many connection is the primary station. The primary station is responsible for the recovery of lost token, to maintain the 500 msec heartbeat, and, in general, the orderly operation of the connection. In addition to the above major procedures, there are many other procedures, for example: sniffing, address conflict resolution, exchange primary/ secondary roles, just to name a few. Collectively, IrLAP provides an orderly and reliable connection between the IR stations. IrLMP Layer The IrDA Link Management Protocol (IrLMP) consists of two components: the Link Management Information Access Service (LM-IAS), and the Link Management Multiplexer (LM- MUX). IrLMP is a mandatory element of the IrDA standard, but again, not all features of IrLMP are mandatory. LM-ISA entity maintains an information base so that other IrDA stations can inquire what services are offered. This information is held in a number of objects, each associated with a set of attributes. For example, "Device" is an mandatory object and has attributes "DeviceName" (an ASCII string) and "IrLMPSupport" (IrLMP version number, IAS support, and LM-MUX support). The other component of IrLMP, LM- MUX, provides multiple data link connections over the single connection provided by IrLAP. Within each IR station, multiple Link Service Access Points (LSAPs) can be defined, each with a unique selector (LSAP-SEL). LM-MUX provides data transfer services between

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HCL Infosystems Limited LSAP-SEL end points within the same IR station as well as across the IrLAP connection to other IR stations. The LM-ISA discuss previously uses a pre-defined LSAP-SEL (0) for other IR stations to access over IrLAP and through LM-MUX. The LM-MUX can be in one of two modes, exclusive or multiplexed. When in exclusive mode, only one LSAP connection may be active. In this case the flow control provided by IrLAP can be used for the only connection. When in multiplexed mode, several LSAP connections may actively share the same underlying IrLAP connection. However, in this case additional flow control must be provided by upper layers or the applications.

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HCL Infosystems Limited IrTP, TinyTP, IrCOMM, and Beyond IrTP and TinyTP are optional transport protocols. The main proposes are to provide individual LSAP flow control functions and to segment or reassemble data. The additional flow control is needed when the LMMUX is in multiplexed mode. The segmentation and reassembly of data is used to match the user buffer size and IrLAP/IrLMP data size. IrCOMM is the protocol to emulate pre-existing wired serial and parallel ports. There are four service types. The 3-wire raw service type emulates a 3wire RS-232 port ( TxD, RxD and Gnd wires with no flow control). It has no control channel and relies on IrLAP for flow control (and hence it must use LM-MUX exclusive mode). The other three service types use TinyTP and have separate control channels. They emulate 3- wire (cooked), 9wire, and Centronics parallel. Other IrDA optional layers include PnP (Plug-and-Play), Obex (Object exchange), and many others. Most of these optional layers are aiming at facilitating the adoption/development of application programs. Physical Layer, IrLAP, and IrLMP are the only layers that are mandatory in the IrDA standard. While these three layers provide the bases for an efficient and reliable link, the design is extensible and open-ended. IrDA has defined and is continuously working on other optional upper layers. External Connection To implement IrDA-1.0 external adapters to be attached to the RS232 serial port, the challenge is to reach a long distance with reliable IR connection sustainable at 115.2Kbps baud rate, using only the limited current supplied from the RS232-port signal lines. This current is typically in the range of 10mA, which needs to be booted up to around 21mA average current at 115.2Kbps rate in order to provide reliable IR communication at distance of 1 meter. For implementing IrDA-1.0 external adapter for printer and other peripherals, compact IrDA protocol stack needs to be built into the adapter. To implement IrDA-1.1 (1.152M and/or 4M bps) external serial adapter, RS232 port is too slow. There are four options: internal add-on card, special IrDA connector, enhanced parallel port, special serial port like Universal Serial Bus (USB), etc. All these options are being explored by many of the current IrDA adapter suppliers. To implement IrDA-1.1 external adapters for printers, peripheral devices or wired LAN, the appropriate IrDA protocol stacks need to be built into the adapters.

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Infrared Q & A What is an IrDA infrared data connection? A cordless data connection using infrared light. It is a low-cost transceiver signaling technology for two way data exchange. It provides high-speed digital exchange through the typical PC UART/serial port at 9600-115200 bits/s, and in some units compatible high speed extensions up to 1Mb/s and 4Mb/s speeds. What are the distance limitations for IrDA-compliant infrared connections? Although the IrDA standard only specifies a connection from zero to one meter, many IrDA-compliant products can connect at distances greater than one meter. Why infrared standards? To ensure interoperability between devices of all types. What is the difference between diffuse infrared, directed infrared, and radio frequency? Diffuse infrared allows many-to-many connections, does not require direct line of sight and can be uni- or bi-directional. Since it is based on visible light, it is a secure form within a room. Financial trading floors are an example of diffuse infrared. Direct infrared is point-to-point, typically one-to-one communications, is not subject to regulations, requires line of sight and is a secure form of data transmission and reception. IrDA is an example of directed infrared. Radio frequency is not secure in that it can penetrate walls, is subject to uncontrolled interference, is typically higher in power than directed infrared and requires FCC certification. How secure is infrared? Very secure. Using infrared connection to access the LAN is as secure as using a cable at any other access point on the network. You need to be an authorized user on the subnet. How reliable is infrared? Often more reliable than wired solutions. When was the last time your TV remote control broke? In fact, we believe that the IR port will prove more reliable than wired connections because we will have eliminated wearand-tear. No pins to bend, no plugs to jam. Does the length of the infrared connection affect the speed of the network? i.e., if the portable is farther away from the network access point, will the connection be slower? To be IrDA-compliant a product must be capable of maintaining a constant connection speed. 15

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HCL Infosystems Limited When will faster infrared speeds be available? You can expect to see 16 Mbps speeds in the near future. Engineers say that even 50Mbps speeds are technology feasible, but won't be available for at least a few years. Why not wait for 16 Mbps speeds? 4Mbps fits the speed and data transmission requirements and is a viable speed for most PC applications today. As file size requirements grow, some segments of the industry will require higher speeds such as high speed LAN's. What products use infrared today? Infrared is showing up in several electronic products, such as PDAs, printers, desktop adapters, notebooks, cameras, Palm devices. What products will implement infrared in the future? Infrared will soon be seen in copiers, fax machines, overhead projectors, telephones, bank ATM's, credit cards, game controls, and headsets. What do I need to be able to use Ir from my laptop to my desktop PC? Your laptop needs to have the appropriate software drivers on it such as Microsoft Ir Monitor, QuickBeam or Transit (application dependent). If your Desktop PC does not have an IR port or software, you will need to get an Ir adapter and software to enable you Desktop. Ir adapters are available on the market today. Please go to the Products page on this web site to determine vendor offerings. What does FIR and SIR stand for? FIR stands for Fast Infrared, which is the capability to transfer data up to 4Mbps. SIR stand for Serial Infrared, which is the capability to transfer data at 115Kbps.

Reference: http://www.irda.org/ http://msdn.microsoft.com/library/default.asp?url=/library/enus/dnirda/html/irdawp.asp http://www.extendedsystems.com/ESI/Products/Wireless+Connectivity+Product s/IrDA+Adapters/

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