I2S

I2S?

Inter-IC Sound, Integrated Interchip Sound, or IIS, is an electrical serial bus interface standard used for connecting digital audio devices together.
The I²S protocol outlines one specific type of PCM digital audio communication with defined parameters outlined in the Philips specification.

I2S Spec (I2SBUS.pdf) 에 소개된 그림을 통해 용어에 대한 정의 및 기본적인 Sound Data전송 방법에 대해 확인합니다.


Figure 1. Simple System Configurations and Basic Interface Timing

• TRANSMITTER : CPU
• RECEIVER : Sound IC ( Sound Codec )
   The system master can be combined with a transmitter or receiver,
   and it may be enabled or disabled under software control or by pin programming.

• SCK (continuous Serial Clock) : bit clock

• WS (Word Select)

  The word select line indicates the channel being transmitted:

• WS = 0; channel 1 (left);
• WS = 1; channel 2 (right).

• SD (Serial Data) : PCM Data

Audio Data 전송을 위해서는 최소 3개의 line(SCK , WS, SD)이 사용됩니다.
이때 TRANSMITTER로 부터 전달되는 SD는 leading edge ( SCK이 Low 에서 High로 변경되는 시점)에 RECEIVER에서 읽어야 합니다.
(Serial data sent by the transmitter may be synchronized with either the trailing (HIGH-to-LOW) or the leading (LOW-to-HIGH) edge of the clock signal.
However, the serial data must be latched into the receiver on the leading edge of the serial clock signal, and so there are some restrictions when transmitting data that is synchronized with the leading edge.)

Sound IC(sound codec)에 입력 장치가 존재할 경우, master clock line 과 upload SD line 을 추가로 사용합니다.

Sound IC 는 자체적으로 Clock을 만들 수 없으므로 master clock을 이용하여 SCK, WS를 생성하여 입력 장치로부터 들어오는 analog sound data를 digital 변환 후 SCK, WS 와 함께 Upload SD Line을 통해 TRANSMITTER로 전달합니다.

(참조 : http://en.wikipedia.org/wiki/I%C2%B2S)

The bus consists of at least three lines:

1. Bit clock line
2. Word clock line - also called word select (WS) or left right clock (LRCLK)
3. At least one multiplexed data line

It may also include the following lines:

1. Master clock (typical 256 x LRCLK)
2. A multiplexed data line for upload

• I2S는 Sound Data 전송을 위한 표준이므로 Sound IC control을 위한 I2C가 함께 연결되어 있어야 합니다.

(이미지 참조 : http://musart.tistory.com/search/I2S)