IIS是飞利浦公司定义的一种用于音频传输的数字总线,LPC1768支持该总线, I2S接口为一条3线串行总线，含有1根数据线、1根时钟线和1根字选择信号线。基本的I2S连接具有一个主机（其总是为主机）和一个从机。LPC1700系列Cortex—M3微控制器的I2S提供了彼此独立的发送和接收通道，每个通道都可作为主机或从机.
使用代码如下
void IISInit(void)
{
//打开IIS时钟
LPC_SC->PCONP |= 1<<27;
LPC_SC->PCLKSEL1 &= ~(0X03<<22); //时钟选择25M
//0.4 IIS RX CLK
LPC_PINCON->PINSEL0 &= ~(0x03u<<8);
LPC_PINCON->PINSEL0 |= (0x01u<<8);
//0.5 IIS RX LR
LPC_PINCON->PINSEL0 &= ~(0x03u<<10);
LPC_PINCON->PINSEL0 |= (0x01u<<10);
//0.6 IIS RX DAT
LPC_PINCON->PINSEL0 &= ~(0x03u<<12);
LPC_PINCON->PINSEL0 |= (0x01u<<12);
//0.7 IIS TX CLK
LPC_PINCON->PINSEL0 &= ~(0x03u<<14);
LPC_PINCON->PINSEL0 |= (0x01u<<14);
//0.8 IIS TX LR
LPC_PINCON->PINSEL0 &= ~(0x03u<<16);
LPC_PINCON->PINSEL0 |= (0x01u<<16);
//0.9 IIS TX DAT
LPC_PINCON->PINSEL0 &= ~(0x03u<<18);
LPC_PINCON->PINSEL0 |= (0x01u<<18);
//mclk IIS TX MCLK
LPC_PINCON->PINSEL9 &= ~(0x03u<<26);
LPC_PINCON->PINSEL9 |= (0x01u<<26);
//FS 48K DATALENGTH 16 MONO ON MCLK 256FS
LPC_I2S->I2STXRATE = 0;
LPC_I2S->I2STXRATE = (98<<8)| 100; //X 98 Y 100 MCLK (25000000/2)*0.98 12250000
LPC_I2S->I2SRXRATE = 0;
LPC_I2S->I2SRXRATE =(98<<8)| 100; //X 98 Y 100 MCLK (25000000/2)*0.98 12250000
LPC_I2S->I2STXBITRATE = 7; //BIT_RATE=MCLK/(7+1)=1531250 FS = 1531250/16/2 = 47.85
LPC_I2S->I2SRXBITRATE = 7; //BIT_RATE=MCLK/(7+1)=1531250 FS = 1531250/16/2 = 47.85
LPC_I2S->I2STXMODE |= 1<<3; //禁止TCLK输出
LPC_I2S->I2SRXMODE |= 1<<3; //禁止RCLK输出
//16位数据 立体声 使能fifo 主模式 采样周期32 仅仅发送0
LPC_I2S->I2SDAO = (1<<0)|(0<<2)|(0<<3)|(0<<4)|(0<<5)|(15<<6)|(0<<15);
LPC_I2S->I2SDAI = ((16-1)<<6)|(0<<5)|(0<<4)|(0<<3)|(0<<2)|(1<<0);
IIS_Stop();
LPC_I2S->I2SIRQ = (0<<0)|(0<<1)|(32<<8)|(32<<16); //32位fifo深度 不使能接受中断,发送中断
NVIC_EnableIRQ(I2S_IRQn);
FillBuffer(Buf_L,1000,Buf_R,1000);
}
void IISStart()
{
LPC_I2S->I2SDAO &= (~(1<<4)); //复位停止访问fifo使能并开始发送
LPC_I2S->I2SDAO &= (~(1<<3));
LPC_I2S->I2SDAO &= (~(1<<15));
}
void IISStartTransData(void)
{
IISStart();
LPC_I2S->I2SIRQ |= LPC_I2S->I2SIRQ | (1<<1);
}
void I2S_IRQHandler(void)
{
u32 state=LPC_I2S->I2SSTATE;
if(state&0x1)
{
if( ((state>>16)&0x1f)==0 )
{
s16 datl=Buf_L[current_l++];
s16 datr=Buf_R[current_r++];
LPC_I2S->I2STXFIFO = (datr<<16) | (datl & 0xFFFF);
if(current_l>=len_l)current_l=0;
if(current_r>=len_r)current_r=0;
}
}
}