Infrared port

The Infrared Data Association (IrDA) is an industry driven interest group that was founded in 1993 by around 50 companies. IrDA provides specifications for a complete set of protocols for wireless infrared communications and the name "IrDA" also refers to that set of protocols. The main reason for using IrDA had been wireless data transfer over the “last one meter” using point and shoot principles. Thus, it has been implemented in portable devices such as mobile phones, laptops, cameras, printers, medical devices and many more. Main characteristics of this kind of optical wireless communication is physically secure data transfer, Line-of-Sight (LOS) and very low bit error rate (BER) that makes it very efficient. The mandatory IrPHY (Infrared Physical Layer Specification) is the physical layer of the IrDA specifications. It comprises optical link definitions, modulation, coding, cyclic redundancy check (CRC) and the framer. Different data rates uses different modulation/coding schemes: SIR: 9.6-115.2 kbit/s, asynchronous, RZI, UART-like, 3/16 pulse MIR: 0.576-1.152 Mbit/s, RZI, 1/4 pulse, HDLC bit stuffing FIR: 4 Mbit/s, 4PPM VFIR: 16 Mbit/s, NRZ, HHH(1,13) UFIR: 96 Mbit/s, NRZI, 8B10B GigaIR: 512 Mbit/s – 1Gbit/s, NRZI, 2-ASK, 4-ASK, 8B10B 5/10GigaIR: seems to be a new IrPHY coming soon[1] Further characteristics are: Range: standard: 1 m; low power to low power: 0.2 m; standard to low power: 0.3 m, The 10 GigaIR also define new usage models that supports higher link distances up to several meters. Angle: minimum cone ±15° Speed: 2.4 kbit/s to 1 Gbit/s Modulation: baseband, no carrier Infrared window Wavelength: 850-900 m The frame size depends on the data rate mostly and varies between 64 Byte and 64 kByte. Additionally bigger blocks of data can be transferred by sending multiple frames consecutively. This can be adjusted with a parameter called Window Size (1-127). Finally data blocks up to 8 MByte can be sent at once. Combined with a low bit error rate of generally <10E-9, that communication could be very efficient compared to other wireless solutions. IrDA transceivers communicate with infrared pulses (samples) in a cone that extends minimum 15 degrees half angle off center. The IrDA physical specifications require that a minimum irradiance be maintained so that a signal is visible up to a meter away. Similarly, the specifications require that a maximum irradiance not be exceeded so that a receiver is not overwhelmed with brightness when a device comes close. In practice, there are some devices on the market that do not reach one meter, while other devices may reach up to several meters. There are also devices that do not tolerate extreme closeness. The typical sweet spot for IrDA communications is from 5 to 60 cm (2.0 to 24 in) away from a transceiver, in the center of the cone. IrDA data communications operate in half-duplex mode because while transmitting, a device’s receiver is blinded by the light of its own transmitter, and thus, full-duplex communication is not feasible. The two devices that communicate simulate full duplex communication by quickly turning the link around. The primary device controls the timing of the link, but both sides are bound to certain hard constraints and are encouraged to turn the link around as fast as possible.