红外线传输方式介绍

红外线传输方式介绍 IRDA 紅外線傳輸方式介紹 2004/09/06Weng 紅外線數據協會(Infrared Data Association;IrDA)是第一個踏入短距離無線通訊領域的世界 組織,於1993年成立, 現在成員已超過一百家,而紅外線的傳輸速度由SIR、CIR(9.6Kbps, 115.2Kbps),只能數據傳送、遙控等弁鉞o展到UFIR(40Mbps),能傳送即時動態畫面,使紅外 線在無線傳輸上的應用除了低價格、錯誤率低、保密性高、耗電量低、低干擾性等優點外,在 速度上也有大幅度的進步,甚至可能因應市場需求,在速度上會增加到100Mbps。 在金融上的交易(IrFM)以及紅外線家電(IrControl)是未來紅外線的主要市場. 無線區域網 路、藍芽這兩者以微波為傳輸方式的無線網路,有一個最大得問題在於非常容易受到電波干擾, 所以只要不是大量傳輸的通訊產品都會選擇內建紅外線傳輸,比較不用擔心資料被擷取以及在 傳送資料時被電波干擾,這也是紅外線在手機、PDA等應用較802.11、藍芽、HOMERF等微 波傳輸廣泛原因之一. The Infrared Model: In an effort to achieve a wireless connection to a full range of peripheral devices without the hassle of cable, infrared technology was born. 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 The IrDA standard: 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. 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. Connecting with IR: Once two infrared devices are within range of each other, Windows 95 will automatically detect the device and display its signature on the screen. An audible alert will also sound indicating a connection has been made. If for any reason the beam is interrupted Windows 95 will again signal audibly and attempt to re-establish the link for up to 45 seconds. No data loss will occur if the link is re-established at that time. "An Introduction to the IrDA Standard and System Implementation" Abstract The IrDA standard has successfully progressed from IrDA-1.0 (115.2Kbps) to IrDA-1.1 (4Mbps) in the short two and half years. There are many components, adapters, software and mobile systems available for the IrDA-1.0 standard on the market now. The same will happen soon for IrDA-1.1 standard with the optoelectronic, analog and digital interface ASIC components already on the market. It is important to understand the difference between IrDA-1.0 and IrDA-1.1 in the physical modulation, protocol, system implementation and external attachment considerations. Introduction Infrared Data Association (IrDA) Infra-red has long been used as a transmission medium for TV/VCR controllers, calculators, printers, and PDAs. In late 1993 an industrial group spearheaded by HP, IBM, and Sharp was founded to promote an industrial standard for Infra-red communications. A short two and half years later, this group, the Infra-red Data Association, has grown to 130 members strong. The membership are international and include component manufacturers, OEMs, hardware and software companies. More impressively, by 1995, many IrDA compliant products are already in the end users' hands. This include IR equipped notebook PCs, PDAs, printers, as well as IR adapters for PCs, printers, etc. According to BIS Strategic Research, by 1996, 85% of the new notebook PCs will have IrDA capability built into the systems. Unlike the earlier IR predecessors which use proprietary protocols, this new crop of IrDA compliant equipments are inter-operative across applications, across manufacturers, and across platforms. The key features of IrDA standard are: , Simple and low cost implementation , Low power requirement , Directed, point-to-point connectivity , Efficient and reliable data transfer 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 30 degree 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 IrDA-1.1. 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 as IrLAP is concerned, connection-less transmission are broadcast in nature and are not acknowledged by the receiver. The discovery procedure defines a 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.) are 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 heart beat, 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 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. 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 LM-MUX 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 3-wire 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), 9-wire, and Centronics parallel. Other IrDA optional layers include PnP (Plug-and-Play), Obex (Object exchange), and many others. Most of these optional layer 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. IrDA-1.0 System Implementation To implement IrDA capability into systems like notebook PCs, PDAs, etc., one needs to use the digital interface chip and an analog front-end component. IrDA-1.0 digital chips in the form of super I/O chips are provided by National Semiconductor, SMC, Winbond, etc. Analog module are in two forms: chips or optoelectronic modules. Analog chips are supplied by Irvine Sensor, Unitrode, Rohm and Crystal Semiconductor (which has an integrated mixed-signal analog/digital chip) where additional IR-LED and detector diode are needed and careful PCB layout around the sensitive detector circuitry is required. Optoelectronic modules are provided by HP, Temic, Siemens, Sharp, etc. which integrate the analog chip with the IR-LED and diode in one compact module with various pinout configurations. The system implementation of IrDA- 1.0 is straightforward. The only inconvenience is the need to implement in IrDA application software (e.g. Windows 95 -IR driver from Microsoft or Tranxit file transfer software from Puma Technology) the respective hardware device driver to program speeds for each hardware systems. For IrDA-enabled portable devices that do not use Windows operating system, special IrDA protocol engine (stack) in either C or assembly codes need to be built in. Due to their limitation of low-power, slow CPU, limited memory, very compact IrDA protocol stack is required. ACTiSYS has successfully licensed their protocol stack in C or various assembly codes (model # ACT- IR920SW-IR960SW) to many OEM manufacturers of cellular phones, pagers, printers, portable instruments, portable storage devices, handheld PCs, etc. The code compactness is represented by one of their model, ACT-IR920SW (8031 code for peripherals) that is only 3.8 KBytes. IrDA-1.1 System Implementation Aside from the differences in the Physical Layer, The IrLAP, IrLMP, and upper layers of IrDA-1.0 and IrDA-1.1 are almost identical. By design, IrDA-1.1 is also backward compatible with IrDA-1.0. However, due to the much higher data rate allowed in IrDA-1.1, there are both hardware and software implications. For the 115.2 kbps top data rate used in IrDA-1.0, most computers and micro- controllers only need very minimum hardware and can use the CPU to handle the byte stuffing or removal and the CRC calculations. Low end micro-controllers such as 22 MHz 80C51 and 12 MHz Z80 has been successfully used to implement IrDA secondary stations at 115.2 kbps. The hardware needed consists of a UART (which most computers and micro-controllers may already have), a simple encoder/decoder circuit and the IR transceiver. For the 1.152M and 4.0 Mbps data rate used in IrDA-1.1, a packetizer must be used and the encoder/decoder circuit is more complex. The IR transceiver must also be capable of handling the faster speed. In most of the cases, DMA needs to be used to transfer data from the packetizer to and from memory. Even through there is no significant changes in the IrLAP, IrLMP, and upper layers of the protocol from IrDA-1.0 to IrDA-1.1, software efficiency must also be considered. For example, at 115.2 kbps, it takes about 100 msec to transmit a 1 KByte frame. Thus a 2 msec software overhead will only cause a 2 % degradation in performance. At 4 Mbps, however, it takes only 2 msec to transmit the same 1 KByte frame and the same 2 msec software overhead will cause a 100 % degradation in performance. In order to take advantage of the higher raw data rate, IrDA-1.1 software must be more efficient or be assisted by hardware. 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. ACTiSYS has successfully accomplished this with their ACT-IR220L serial adapter which offers 2.4 meter reliable IR link distance in most applications using no external power. For the Japanese market where ASK- IR modulation and protocol specification has long been used in consumer electronic devices like organizers, etc. It is very desirable to have both IrDA and ASK dual modes in the IR interface device. One example is the ACTiSYS ACT-IR200L dual- mode serial adapter. It also maintains the company tradition of long IR communication distance using only RS232-port signal power and no external power source. For implementing IrDA-1.0 external adapter for printer and other peripherals, compact IrDA protocol stack needs to be built into the adapter. Some examples are ACTiSYS's ACT-IR100X and IR100M printer adapters. 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. Example is ACTiSYS's ACT-IR2000 series. 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. Examples are the LAN adapter from Extended Systems and ACTiSYS (ACT- IR1000M and IR6000N). System Hardware Testing The common problem faced by many of the IrDA-enabled systems manufacturers is the long IrDA test bottleneck on the production line. They usually use the commercially available IrDA-compliant application software or even the non-IrDA compatible file transfer software. To shorten the test time, they use very short test file. The problem is long test time (~1 minute), no easy reading and unreliable test of error rate at different speeds, no parameter re- setting by QA engineer, no isolation of send or receive problem, no automatic recording of test results. Recently, there are specific IrDA system hardware test software available to solve all these critical problem. Example is ACTiSYS's ACT-IR900SW which requires 5~10 sec. per test system to automaticall print and record the error rates. It has special test patterns to exercise stress test on IrDA hardware. It can even test both IrDA and ASK modes. Its extension, IR9000SW will test IrDA-1.1 enabled system hardware and is being tested on the newly available IrDA-1.1 adapters. Conclusion We have described here the basics of IrDA-1.0 and IrDA-1.1 protocol, system implementation, external connection and system hardware testing. The components for both IrDA generations will become easily available and their cost reduced very quickly. The percentage of IrDA-enabled mobile and desktop computers will increase very quickly. This will expand soon into the various vertical markets of non-computer industries. The IrDA-compliant application software, the protocol stacks for controller environment and system hardware testing software have been the show stopper. This situation is improving quickly and should accelerate the rate of IrDA implementation into new systems. Many new IrDA applications in video conferencing, ISDN-, PBX-link will also emerge. The new challenge for IrDA community is the incorporation of and co- existence with consumer IR (usually longer distance, higher power and lower baud rate) applications and future higher speed (perhaps 15 Mbps or higher) extension. Introduction to IrDA IrDA is a standard defined by the IrDA consortium (Infrared Data Association). It specifies a way to wirelessly transfer data via infrared radiation. The IrDA specifications include standards for both the physical devices and the protocols they use to communicate with each other. The IrDA standards have arised from the need to connect various mobile devices together. (Primary use for IrDA is to link notebooks or various personal communicators; however, even video cameras are sometimes equipped with an IrDA interface.) IrDA devices communicate using infrared LED's. Wavelength used is 875 nm +- production tolerance (around 30 nm). Many CCD cameras are sensitive to this wawelength too. Receivers utilize PIN photodiodes in generation mode (incoming light "kicks out" electrons. Signal continues into a filter. Only allowed frequencies for a particular IrDA modulation can pass through.) There is a direct relationship between the energy of the incoming radiation, and the charge that the optics part of the receiver generates. Range and speed of IrDA IrDA devices conforming to standards IrDA 1.0 and 1.1 work over distances up to 1.0m with BER (Bit Error Ratio - number of incorrectly transferred bits over number of correctly transferred bits) 10-9 and maximum level of surrounding illumination 10klux (daylight). Values are defined for a 15 degree deflection (off-alignment) of the receiver and the transmitter; output power for individual optical components is measured at up to 30 degrees. Directional transmitters (IR LEDs) for higher distances exist; however, they don't comply with the required 30 degree radiation angle. Speeds for IrDA v. 1.0 range from 2400 to 115200 kbps. Pulse modulation with 3/16 of the length of the original duration of a bit is used. Data format is the same as for a serial port - asynchronously transmitted word, with a startbit at the beginning. Transmitter can use either 3/16 mark-to-space ratio for one bit, or a fixed length 1.63 us of each optical pulse, which would correspond to 115kbps. With fixed length and speed of 38400 bps, each bit would take 3 pulses. In addition, IrDA v. 1.1 defines speeds 0.576 and 1.152 Mbps, with 1/4 mark-to-space ratio. At these speeds, the basic unit (packet) is transmitted synchronously, with a starting sequence at the beginning. The NRZ signal in the figure is the original data signal without modulation. A packet consists of two start words followed by target addres (IrDA devices are assigned numbers by the means of IrDA protocol, so they are able to unambiguously identify themselves), data, CRC-16 and a stop word. The whole packet (frame) including CRC-16 is generated by IrDA compatible chipset. Start and stop words cannot appear anywhere else in the data stream - start and stop words last 1.5times the bit duration (6 times longer flash than usual). For 4Mbps speed, so-called 4PPM modulation with 1/4 mark-to-space ratio is used. Two bits are encoded in a pulse within one of the four possible positions in time. So, information is carried by the pulse position, instead of pulse existence as in previous modulations. For example, bits 00 would be transmitted as a sequence 1000 (flash-nothing-nothing-nothing), bits 01 would be 0100, bits 11 would be send as 0001. Main reason for the 4PPM modulation is the fact, that only half of the LED flashes are needed than in previous modulations; so, data can be transferred two times faster. Besides, it is easier for the receiver to maintain the level of surrounding illumination - with the 4PPM modulation, a constant number of pulses is received within a given time. With bit speed of 4Mbps, the transmitter flashes at 2MHz rate. However, unlike 0.576 and 1.152 Mbps, 4Mbps packets use CRC-32 correction code. Most chipsets which can use this modulation can also generate CRC-32 by themselves, and check it when receiving - some chipsets (the ones I have studied) throw away incorrectly received frames. More, IrDA defines so-called low-power IrDA device, with range up to 20 cm and max. speed 115kbps (a.k.a. IrDA 1.0). Limiting factor for the range is the radiation intensity at the receiver in mW/cm2. This value is higher for faster bit speeds, for slower bit speeds (long pulses) the possible range increases. (This is not explicitly mentioned in the IrDA standards, but it correlates to the amount of incoming radiation - receiver thinks that short low-energy pulses are noise. For its filter to let them through, they need to be either longer, or their energy must be higher.) Why a pulse modulation is used? The receiver needs a way to distinguish between the surrounding illumination, noise, and received signal. For this purpose, it is useful to use the highest possible output power: higher power -> higher current in the receiver -> better signal-to-noise ratio. However, IR-LED's can't transmit at full power continuously over 100% of time. So, a pulse width of only 3/16 or 1/4 (mark-to-space ratio) of the total time for one bit is used. Now, the power can be up to 4 or 5 times the possible maximum power for LED's shining continuously. In addition, the transmission path does not carry the dc component (since the receiver continuously adapts itself to the surrounding illumination, and detects changes only.), thus it is necessary to use pulse modulation. Integrated IrDA transceivers (combined transmitting IR-LED and the receiving PIN photodiode) do have filters that eliminate noise other than the IrDA frequency range 2400-115200 bps and 0.576-4Mbps (2M flashes/s). Protocols used by IrDA devices , IrDA Infrared Link Access Protocol (IrLAP) is a modification of the HDLC protocol reflecting the needs of IrDA communication. In general, it encapsulates the frames and makes sure the IrDA devices don't fight among themselves - in multi-device communication, there is only one primary device, others are secondary. Note that the communication is always half-duplex. Also, IrLAP describes how the devices establish connection, close it, and how are they going to be internally numbered. Connection starts at 9600 Bd; as soon as information about supported speeds is exchanged, logical channels (each controlled by a single primary device) are created. , IrDA Infrared Link Management Protocol (IrLMP) Since configuration of IrDA devices changes (you turn on your IrDA camera and put it next to your notebook), every device lets the others know about itself via the IrLMP protocol, which runs above IrLAP (IrLAP is a link protocol; I would compare it to the IP protocol, although address resolution is different). IrLMP's goal is to detect presence of devices offering a service, to check data flow, and to act as a multiplexer for configurations with more devices with different capabilities involved (compare to sockets in TCP/IP communication). Then, applications use the IrLMP layer to ask if a required device is within range, etc. However, this layer does not define a reliable way to create a channel (like in TCP); this is defined by IrDA Transport Protocols (Tiny TP). , IrDA Transport Protocols (Tiny TP) This layer manages virtual channels between devices, performs error corrections (lost packets, etc.), divides data into packets, and reassembles original data from packets. It is most similary to TCP. , IrDA Object Exchange Protocol (IrOBEX) is a simple protocol, which defines PUT and GET commands, thus allowing binary data transfer between devices. It is built on top of TinyTP. The standard defines what a packet must contain in order for the devices to recognize each other and communicate. , Extensions to IrOBEX for Ir Mobile Communications This extension of IrOBEX for mobile devices - handhelds, PDA, cellular phones - defines how to transfer informations pertaining to GSM network (address books, SMS, calendar, dialing control, digital voice transfer over IR, ...) IrTran-P (Infrared Transfer Picture) Specification This definition was made up by big companies manufacturing digital cameras and specifies how to transfer pictures over the infrared interface. It is built on top of TinyIP, too. IrDA components Here, I can describe my own experience with several components made by Hewlett Packard. They manufacture stand-alone IrDA transmitters (IR LED), receivers, as well as transceivers (a receiver with a transmitter in a single package). For speeds up to 115kbps (IrDA 1.0), HSDL-1000 transceiver is available. It works in half-duplex mode. It is very easy to use. Besides the transceiver itself, only several capacitors to filter the signal and to reduce noise are used. The capacitors need to be placed as close to the transceiver as possible, preferably within 0.7 cm (0.3 in). Since the HSDL-1000 is in a SMD package, it is a good idea to place it on a two-layer PCB, with ground copper area on the other side for shielding. A faster version of the transceiver is labelled HSDL-1100. It supports FIR speeds (up to 4Mbit/s). However, I had problems with this one. In improper design, the FIR output easily becomes an oscillator. This part is also more sensitive to noise and unwanted feedbacks than the HSDL-1000 (FIR output only). Other HP components available include IR LEDs HSDL-4230 and HSDL-4220. These LEDs withstand modulation speed up to 10Mbits, maximum current 0.5A (mark-to-space ratio 0.2) or 100mA (continuously). The only difference of the two versions in the HSDL-4200 family is their radiation angle (30 degrees for HSDL-4220, only 17 degrees for HSDL-4230). Also, Hewlett-Packard manufactures standalone PIN receivers as well as IrDA modulation encoders/decoders. Integrated encoder/decoder of IrDA 115kbps modulation can be ordered under part No. HSDL-7000. It is an integrated circuits with 8 pins. In addition to power, serial port transmit/receive, a 16-times the bit frequency oscillator needs to be connected to it (for 115kbps, required frequency is 115200*16=1.8432 MHz). I had a chance to try out encoder/decoder HSDL-7001; however, it offers only a few additional functions (e.g. integrated frequency divider, or a possibility to connect a passive XTAL directly to its inputs). In addition, the integrated frequency divider works for IR input only, not for the output. Of course, Hewlett-Packard is not the only manufacturer of IrDA components. For example, Texas Instruments manufactures UART's labeled TIR1000 and TIR2000. The TIR2000 incorporates a driver for the 4Mbps modulation (uses DMA mode). National Semiconductors produce their own versions. And so on. In the Czech Republic, UARTs by TI and NS circuits are probably the most commmon ones. Links to manufacturers of IrDA components Here are links to WWW pages of different IrDA devices manufacturers. , IBM Hewlett Packard HP ir chip directory HP ir center Texas Instruments National Semiconductor PC87109 Vishay-Telefunken (drive Temic) Nemecko Vishay-Telefunken (drive Temic) USA , Linux support for IrDA I don't have to mention IrDA protocol support at Micro$oft. However, here is a link to The Linux/IR Project, whose objective is to incorporate IrDA protocols into Linux kernel. Source codes are tested on development Linux kernels (2.1.xxx), (2.1.xxx) Practical experiences When playing with the IrDA data transfer, our goal was far beyond the 1 meter range specified by the IrDA standard. Using IR LED's with half the radiation angle (17 degrees, instead of 30), we could go up to 4 meters without additional optics at 115 kpbs bit rate. Beyond a certain distance, the receiver tends to loose individual pulses, or decrease their amplitude and duration (after all, it is an analog circuit although its output is supposed to be "digital"). For greater distances (our requirement was to transfer data over a 200m distance), additional optics is needed. We have found that, if speed is decreased 4 times, distance can be increased two times. This confirms the thesis about pulse detection via certain amount of energy passing through the filter in the receiver. Since our goal was to connect two Linux boxes and run ppp protocol over a serial line, we have created additional logic (1 gate ;). It would continuously send pulses while DTR signal remained inactive, and thus signal a 'hang-up' to the other side. A side effect is that if the serial cable from the computer to the IrDA link is pulled out, the circuit starts sending pulses - as if the computer had hanged up via the DTR signal. This can be used in debugging process - finding signal. More, transmitter can be connected to the receiver on one side, creating a several hundred meters long loopback - ideal for checking connection quality in both directions, without the need to run there and back. With the additional optics, we have found after some time that for distances less than about 80 meters (115 kBd speed), full-duplex mode cannot be used since the transmitted beam reflects back and creates echos. The same applies whenever there is a reflective object in the signal path - a window, for instance. Alignment of the link is critical. The mount has to be very firm, and able to fine-point the components, so they are co-axial. Reasonable bit errors can be achieved if the link is aligned within about one meter (distance 200m - corresponds to approx. one half of a degree angle). Alignment is critical for the transmitter, not the receiver. Our best result was about 0.0006% faulty packets (MTU=296 bytes, ping packet length 64 bytes), in other words, about one packet out of 170000 packets is bad. The statistics for the other direction were about four times worse - bad alignment. Normal rain is obviously not an issue (it has been raining for two days already), problems arise with heavy rain or direct sunshine to the optics. ppp0 Link encap:Point-to-Point Protocol inet addr:10.1.2.4 P-t-P:10.1.1.4 Mask:255.255.255.0 UP POINTOPOINT RUNNING MTU:296 Metric:1 RX packets:49724542 errors:233 dropped:233 overruns:0 frame:0 TX packets:49625500 errors:0 dropped:0 overruns:0 carrier:0 coll:0 This is our ppp line statistics, 115kbps, full duplex, rain, 200m ppp0 Link encap:Point-to-Point Protocol inet addr:10.1.2.4 P-t-P:10.1.1.4 Mask:255.255.255.0 UP POINTOPOINT RUNNING MTU:296 Metric:1 RX packets:25255596 errors:18 dropped:18 overruns:0 frame:0 TX packets:25276229 errors:0 dropped:0 overruns:0 carrier:0 coll:0 and this one with good weather and a different setting (again 200m) Pictures in the text are from WWW pages of Hewlett Packard, Texas Instruments, and bitmap version of pdf documents by IrDA consortium. For pricing information of IrDA components, please contact your local electronics components dealer. USB to IRDA ADAPTER USB to IrDA Infrared Mini Adapter, SIR, MIR, FIR Supported IrDA Modes: ASK SIR (2.4 Kbps to 115.2 Kbps) MIR (576 Kbps to 1152 Kbps) FIR (4 Mbps) UFIR高速紅外線傳輸方式Marketing Requirement for UFIR Proposal to study a new physical rate over 100Mbps October 14, 2002 Waseda University NTT Corporation Background The network environment at home or small office is drastically changed in the recent years. Especially, the access network is changed to IP-based network from telephone-based network by xDSL technology or FTTH (Fiber To The Home) technology; therefore the performance is improved to over 100 Mbps. Unfortunately, the user cannot always access these kinds of high-speed network. Usually, the user has to access the network from PC at office or home. Therefore many large contents were saved on PC. These contents are often used on the other environment. For example, music content is used on portable music player for mobile use. Therefore the quick and easy measure to transfer the content between PC and the other equipment is needed. In the other case, the user want to use high-speed network environment outside of home or office. The mobile phone can access the network anywhere. But the access speed is up to 2 Mbps in the case of IMT-2000. The speed is not enough for the large and rich content such as video. Furthermore the cost of mobile phone based service is very expensive. Recently, we can find RF wireless LAN hotspot service in coffee shops or fast-food restaurants. Hotspot service can be placed as a countermeasure for reasonable mobile access. Last One-feet Problems RF wireless LAN is very convenient to access the high-speed network. But there are two problems of the RF wireless LAN hotspot. One problem is about power consumption. And the other problem is access speed. The RF wireless LAN NIC consumes the electricity very quickly. For example, the typical battery capacity for PDA is 500mAh. The operation current of RF wireless LAN interface card is 500mA. So the operation time of PDA with RF wireless LAN is less than one hour. It is too short for mobile use. The RF wireless LAN of 5GHz band provides up to 50Mbps speed. But the speed is not enough to relay between the high-speed network and RF wireless LAN. The power consumption of IrDA connection is smaller than RF wireless LAN. Unfortunately, IrDA standard supports the physical rate up to 16 Mbps. Therefore, we don’t have the measure of quick and easy connection between high-speed network and the mobile equipment. There is the last one-foot problem. The proposal of 100M-Ir We think the measure of quick and easy connection between high-speed network and the mobile equipment is faster infrared connection than VFIR. The physical rate of the high-speed network is over 100 Mbps. Therefore; the target physical rate is 100 Mbps. For example, if the content is MPEG1 or MPEG4 video, the size of the content is 100-200 MB an hour. When the one-hour content is transmitted on 16 Mbps connection, the transmission time takes 50-100 seconds for transmission. We cannot wait for the point and shoot time more than 30 seconds. When the content is transmitted on 100 Mbps connection, it takes 8-16 seconds. Marketing Impact of UFIR There is no wireless connection product over 100 Mbps in this period. The competitor of 100M-Ir is RF wireless LAN such as 802.11a. It is difficult to improve the physical rate on the radio wave technology. On the other hand, we can realize the physical rate over tera-bits on optical fiber network. The problem is only the eye-safe characteristics. However we already solved the problem by the eye-safe laser technology. And the eye-safe laser can be produced the same technology level as the pick-up device for portable CD player. Therefore, 100M-Ir is a shortcut to solve the last one-foot problem. Other Infrared Advantage For example, the user pays and downloads the content from vending machine on the street. These applications don’t have to be fixed connection. Therefore, the best way for the applications is Infrared ad-hoc connection by point & shoot capability on IrDA standard. IrDA has Ir-FM as the payment measure. The combination of Ir-FM and 100M-Ir with IrBurst can be provided very smart vending service on Infrared connection. We think the combination will be produced the next generation of IrDA applications. Discussion Items The major discussion items are as follows. (1) The characteristics of the device [1] Eye-safe characteristics [2] Wave-form characteristics [3] Maximum transmission rate (Target rate is over 100Mbps) (2) The coding method on physical layer [1] Synchronization method [2] Framing method (Easy coding method for implementation, for example 8B10B) [3] Error detection/correction method (3) The compatibility with VFIR, FIR and SIR [1] The supported range for compatibility [2] Transition Procedure between UFIR and the other physical rates [3] Consideration of IrLAP, IrLMP and TTP (4) Recommended implementation to keep the over 100 Mbps performance [1] Recommendation to the upper layer protocols [2] Recommended use of the UFIR protocols for applications Schedule (1) October 2002 Set up a new SIG, start discussion. (2) June. 2004 Specification Documents Voting for Directional and Draft (3) Early 2005 Final version of Specification Documents Voting for Final