Standards
Sony manufactured a number of consumer devices of different types that share a common proprietary protocol, called S-link. A jack on each device allowed the remote control signals to be interconnected between devices. The protocol included the useful but unusual feature of supporting more than one of the same type of device (such as multiple CD changers). Some A/V components could generate informational status codes that could be used to do things like automatically stop your tape deck when the CD you were recording stopped playing. Software running on a PC with a suitable interface could also control the A/V components and monitor their activity; for example, your computer could tell what disk and track were playing in your CD changer and look up the titles in one of the internet CD databases. Sony charges 5000 USD for access to the S-Link documentation. Sony use the SIRC protocol for remote controls. SIRC is developed in three different versions: 12 bit, 15 bit and 20 bit. After 12 bits have been received, the receiver is waiting if there're coming more falling edges to know if the SIRC protocol is 15 bit or 20 bit coded.
The RC-5 and RECS-80 codes developed by Philips have been casually referred to as international standards. However, the RECS-80 protocol was prone to interference and was quickly replaced by the RC-5 protocol. Although it appears that they were proprietary protocols developed by Philips, they were also adopted by various other manufacturers, specifically European- and US-based ones. This allowed interoperability between the remote handsets and equipment of various brands. The RC-5 code was, and still is, used by many US- and European-based manufacturers of specialty audio/video equipment. Unfortunately, documentation of the standard commands were not widely distributed. Therefore, there are some brands of equipment that use non-standard commands, causing interference with other equipment also using the RC-5 protocol.
The RC-5 command set was defined in the late 1980s and expanded to increase the number of commands in the early 1990s (sometimes called RC-5x). However, the rapidly expanding requirements for newer categories of electronics products since that time (e.g., DVD players, cable boxes, DVR's, et cetera) has led Philips to replace the RC-5 protocol with the newer RC-6 protocol that has both an expanded set of devices (256 versus 32) and commands per device (256 versus 64 in RC-5 and 128 in RC-5x). Again, information on the RC-6 protocol is not readily available from Philips.
In contrast, the major Japanese consumer electronics manufacturers almost universally adopted a protocol that was developed and administered by NEC. In the NEC protocol, each manufacturer is assigned a unique code that is contained in the transmitted command, avoiding the possibility of false triggering by other remote handsets.
RECS-80 uses pulse position modulation and RC-5 uses bi-phase. Early dedicated-purpose chips were offered by Philips Semiconductors to allow for the easy use of RECS-80 and RC-5 protocols. The SAA3004, SAA3007, and SAA3008 encoder chips used RECS-80, and the SAA3006 and SAA3010 encoder chips used RC-5. The SAA3049A decoder chip decoded either type. (Note that the Philips Semiconductors division is now NXP). All of these chips have been discontinued. However, these transmission protocols are easily created and/or decoded with general-purpose 8-bit microcontrollers, such as those offered by Microchip Technology and Atmel.
Transmission of the IR commands requires only a microcontroller and an infrared LED, available from a wide variety of sources. Reception of the modulated commands for RC-5, RC-6, and the NEC protocols is easily accomplished with specialized IR receivers, most readily available from Sharp Corporation and Vishay Intertechnology. These receivers include a photo-diode, an automatic gain control (AGC) circuit, and a demodulator. The demodulated signal is then decoded with a microcontroller.
CEA-931-B defines a method for encapsulating remote control codes over IP and CEA-931-A defines a method for encapsulating remote control codes over IEEE-1394 . These documents are not free even though free standards are the norm for Internet Protocols and contributed significantly to their widespread adoption.
Read more about this topic: Consumer IR, Protocol Description
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