IrDA - Infrared Data Association
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IrDA Short for Infrared Data Association, a group of device manufacturers that developed a standard for transmitting data via infrared light waves. Increasingly, computers and other devices (such as printers) come with IrDA ports. This enables you to transfer data from one device to another without any cables. For example, if both your laptop computer and printer have IrDA ports, you can simply put your computer in front of the printer and output a document, without needing to connect the two with a cable. IrDA ports support roughly the same transmission rates as traditional parallel ports. The only restrictions on their use is that the two devices must be within a few feet of each other and there must be a clear line of sight between them. Formally termed IrBus, now called IrDA. The specification defines the physical (PHY), Media Access Control (MAC), and Logical Link Control (LLC) layers. The physical layer only defines the optical portion of the transmission. IrDA uses the same (asynchronous) data rates as RS-232. Normal data transfers start at 9600 until the transfer rate of the device can be determined. The transfer then moves to the new higher rate. Possible data rates are: 2400, 9600, 19200, 38400, 57600, 115200, 576000, 1152000, and 4000000 bits per second. The transmission uses RZI, and includes bit stuffing to allow devices to remain synchronized for all speeds other than 4Mb/s. At 4Mbps Pulse Position Modulation (PPM) is used. The higher the data rate the smaller the bit time / pulse duration. Uses the standard serial data transmission; 1 start bit, 8 data bits, 0 parity bits, 1 stop bit. Data is transmitted LSB first. CRC is included; 8 bits (CRC-8) for a short packet, or 16 bits (CRC-16) for a long packet. |
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