NEC IR Remote Control Interface with 8051 Revision as of 17:45, 29 July 2016 by Explorer (Talk | contribs) (diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)

IR Remote Controllers and receivers follow standard protocols for sending and receiving the data. Some of the standard protocols are NEC , JVC , SIRC (Sony Infrared Remote Control) etc. We will be discussing only the NEC protocol. After understanding the frame format of IR Remote, We will be interfacing a IR receiver with 8051 and decode the key pressed.

NEC Protocol

NEC IR protocol encodes the keys using a 32bit frame format as shown below.

NEC Frame Format
Address	Complement of Address	Command	Complement of Command
LSB-MSB(0-7)	LSB-MSB(8-15)	LSB-MSB(16-23)	LSB-MSB(24-31)

Each bit is transmitted using the pulse distance as shown below.
Logical '0': A 562.5µs pulse burst followed by a 562.5µs space, with a total transmit time of 1.125ms
Logical '0': A 562.5µs pulse burst followed by a 1.6875ms space, with a total transmit time of 2.25ms

When a key is pressed on the remote controller, the message transmitted consists of the following, in order:

1. A 9ms leading pulse burst (16 times the pulse burst length used for a logical data bit)
2. A 4.5ms space
3. The 8-bit address for the receiving device
4. The 8-bit logical inverse of the address
5. The 8-bit command
6. The 8-bit logical inverse of the command
7. A final 562.5µs pulse burst to signify the end of message transmission.

The four bytes of data bits are each sent least significant bit first. Figure 1 illustrates the format of an NEC IR transmission frame, for an address of 00h (00000000b) and a command of ADh (10101101b).

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Code and Explanation will be updated soon..