I2S Bus Introduction

I2S Bus
The I2S has 3 main signals: 1. Serial clock SCLK, also called bit clock (BCLK), which corresponds to each bit of digital audio, SCLK has 1 pulses. SCLK frequency =2x Sampling frequency x sample number of bits 2. Frame clock Lrck, used to toggle the left and right channel data. A Lrck of "1" indicates that the data being transmitted is the left channel, and "0" means that the data being transmitted is the right channel. The frequency of the Lrck equals the sampling frequency. 3. Serial data sdata, which is the audio data expressed in twos complement. I2S (Inter-ic Sound bus) is a bus standard developed by Philips for audio data transmission between digital audio devices. In the Philips I2S Standard, both the hardware interface specification and the format of the digital audio data are specified. The I2S has 3 main signals: 1. Serial clock SCLK, also called bit clock (BCLK), which corresponds to each bit of digital audio, SCLK has 1 pulses. SCLK frequency =2x Sampling frequency x sample number of bits 2. Frame clock Lrck, used to toggle the left and right channel data. A Lrck of "1" indicates that the data being transmitted is the left channel, and "0" means that the data being transmitted is the right channel. The frequency of the Lrck equals the sampling frequency. 3. Serial data sdata, which is the audio data expressed in twos complement.

Sometimes in order to better synchronize between the system, but also need to transmit a signal mclk, called the main clock, also known as the system clock (Sys clock), is the sampling frequency of 256 times times or 384 times times. A typical I2S signal is shown in Figure 3.

In I2S format, regardless of the number of valid data, the highest bit of data always appears at the 2nd SCLK Pulse after the Lrck change (that is, the beginning of a frame). This makes it possible to have a different number of significant digits from the receiving end to the sender. If the receiver can handle the number of significant bits less than the sender, you can discard the data frame redundant low-level data, if the receiver can handle more significant number of bits than the sender, you can self-complement the remaining bits. This synchronization mechanism makes the interconnection of digital audio devices more convenient and does not result in data dislocation.

[with the development of technology, in the unified I2S interface, there are many different data formats. Depending on the location of the sdata data relative to the Lrck and SCLK, it is divided into left-aligned (less-used), i2s format (i.e., Philips-defined format) and right-aligned (also called Japanese format, normal format).

In order to ensure the correct transmission of digital audio signal, the transmitting end and receiver should adopt the same data format and length. Of course, the length of the data can be different for the I2S format