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COMPUTER Infrared Transceiver for the PC (1) combined remote control and data link Design by B. Kainka This article does more than just describe an IR transceiver that you can use with your PC for remote control and data transfer. Based on the successful Elektor Electronics `PC Peripheral Design' series, it also provides information about the principles of the infrared transfer technique used and interface technology, which you can use for your own projects. that appeared in the `PC Serial peripheral Design' course (Elektor Electronics 9/2000 through 3/2001). Infrared remote controls for television sets, video recorders and other entertainment electronics devices frequently use the Philips RC5 standard. It is easy to determine whether a particular remote control employs RC5 by using the program described in this article. This standard employs light signals modulated at a frequency in the range of 30 to 40 kHz. The remote control unit transmits `bursts', which are individual pulse packets. In our case, these bursts have a duration of either 0.888 ms or 1.776 ms. At a modulation frequency of 36 kHz, a short burst contains 32 individual pulses, while a long burst contains 64 pulses. A complete data packet has a duration of approximately 25 ms and is repeated every 100 ms as long as a button is held depressed. An infrared remote control unit can easily be used for other purposes. For example, it can be used to control certain functions of your own program. A typical application is Infrared data transfer is becoming increasingly more important. Television remote controls use infrared light, but so do PC mice, keyboards, printers and other peripherals. Infrared light is also used in fibre-optic cables. In a sense, the PC infrared transceiver presented here is a practical application that represents a continuation of the series of articles on PC interfaces and Visual Basic 62 Elektor Electronics 1/2002 COMPUTER D2 IC1 78L05 IR Transceiver R1 4k7 R2 4k7 C2 100n D1 2x 1N4148 K1 1 6 2 7 3 8 4 9 5 GND D7 RxD RTS TxD CTS DTR D6 4µ7 C1 25V IC3 T1 R3 100k 1 3 BC547 2 R8 22 C5 TSOP1836 DB9 D3 2x 1N4148 Technical specifications ­ Reception frequency: 30, 33 or 36 kHz, depending on the IC version fitted ­ Transmission frequency: 30­40 kHz, continuously adjustable ­ Power supply: from the serial interface ­ Range: approx. 10 m ­ IR receiver: for remote control per the RC5 standard ­ IR transmitter: RC5 compatible ­ IR data transceiver: serial data, 2400 baud max. 1µ 25V 1N4148 R7 1k C4 22n R5 4k7 D5 D4 P1 2k5 R4 470 7 DIS 8 4 R 1 2 3 IC1 6 2 C3 1 10n THR TR OUT 3 R6 27k T2 T3 555 CV 5 BC337 BC547 010052 - 11 Figure 1. Schematic diagram of an IR transceiver for connection to the serial interface of a PC. controlling a PC slide show. After starting the program, you can sit back and operate everything from where you are sitting. Transceiver hardware Thanks to the availability of integrated receivers, the reception of standard in