一：<略>
二：按照2ch-in，2ch-out，DSD out，修改的audioin_deliver()的部分内容
{
#if (I2S_CHANS_ADC != 0)
/* Input previous L sample into L in buffer */
/* First input (i.e. frameCount == 0) we read last ADC channel ofprevious frame.. */
unsigned buffIndex = !readBuffNo;
#pragma loop unroll
{ // p_i2s_adc[0] :> sample;
// Manual IN instruction sincecompiler generates an extra setc per IN (bug #15256)
asm volatile("in %0,res[%1]" : "=r"(sample) :"r"(p_i2s_adc[0]));
tempsample=bitrev(sample);
/* Note the use of readBuffNochanges based on frameCount */
if(buffIndex)
samplesIn_1[0] =tempsample;//bitrev(sample); // channels 0, 2, 4.. on each line.
else
samplesIn_0[0] =tempsample;//bitrev(sample);
}
#endif
xscope_int(PLVALUE,tempsample);
/* LR clock delayed by one clock, This is so MSB is output on thefalling edge of BCLK
* after the falling edge on which LRCLK was toggled. (see I2S spec) */
p_lrclk <: 0x80000000;/* Generate clocks LR Clock low - LEFT */
#pragma xta endpoint "i2s_output_l"
#if (I2S_CHANS_DAC != 0) && (NUM_USB_CHAN_OUT != 0)
#pragma loop unroll
/* Output "even" channel to DAC (i.e. left) */
{
p_i2s_dac[0] <:bitrev(samplesOut[0]);
}
#endif
doI2SClocks(divide);/* Clock out the LR Clock, the DAC data and Clock inthe next sample into ADC */
#if (I2S_CHANS_ADC != 0)
/* Channels 0, 2, 4.. on each line */
#pragma loop unroll
{
/* Manual IN instruction since compiler generates an extra setc per IN(bug #15256) */
asm volatile("in %0,res[%1]" : "=r"(sample) :"r"(p_i2s_adc[0]));
tempsample=bitrev(sample);
if(buffIndex)
samplesIn_1[1] = tempsample;//bitrev(sample);// channels 1, 3, 5.. on each line.
else
samplesIn_0[1] =tempsample;//bitrev(sample); // channels 1, 3, 5.. on each line.
}
#endif
xscope_int(PRVALUE,tempsample);
p_lrclk <: 0x7FFFFFFF;/* Generateclocks LR Clock high - RIGHT */
#pragma xta endpoint "i2s_output_r"
#if (I2S_CHANS_DAC != 0) && (NUM_USB_CHAN_OUT != 0)
/* Output "odd" channel to DAC (i.e. right) */
#pragma loop unroll
{
p_i2s_dac[0] <:bitrev(samplesOut[1]);
}
#endif
doI2SClocks(divide);
} // !dsdMode
三：进一步的修改：去掉不必要的预编译，用循环代替类似段
(1)#pragma loop unroll命令，编译器在进行编译时，遇到该命令就会对循环进行展开。
由于已经去掉循环，因此可将这一条预编译命令去掉。
(2)#pragma xtaendpoint "i2s_output_r" ，xta是另一种芯片，带ARM核，因此可去掉。
(3)用循环表示左右声道的处理，将类似的两段代码写成一段，注意用#pragma loop unroll预编译指令展开
(4)用了两个数组（samplesIn_1[],samplesIn_0[]）来存储录音数据，注意从I2S读入的是一个数组，而DoSampleTransfer中用的是另一个数组。
{
int i=0;
#pragma loop unroll //预编译命令,将下面循环展开
for(i=0;i<2;i++) //i=0: even channel left;i=1:odd channelright.
{
/* Input previous Lsample into L in buffer */
/* First input (i.e.frameCount == 0) we read last ADC channel of previous frame.. */
unsigned buffIndex = !readBuffNo;//(frameCount< 3) ? !readBuffNo : readBuffNo;
// p_i2s_adc[0] :>sample;
// Manual IN instructionsince compiler generates an extra setc per IN (bug #15256)
asm volatile("in %0,res[%1]" : "=r"(sample) : "r"(p_i2s_adc[0]));
tempsample=bitrev(sample);
/* Note the use ofreadBuffNo changes based on frameCount */
if(buffIndex)0
samplesIn_1[i] = tempsample;//bitrev(sample);
else
samplesIn_0[i] =tempsample;//bitrev(sample);
/* LR clock delayed byone clock, This is so MSB is output on the falling edge of BCLK
* after the falling edge on which LRCLK wastoggled. (see I2S spec) */
if(i==0)
{
xscope_int(PLVALUE,tempsample);
p_lrclk <: 0x80000000;/* Generateclocks LR Clock low - LEFT */
}
else if(i==1)
{
xscope_int(PRVALUE,tempsample);
p_lrclk <: 0x7FFFFFFF;/* Generate clocks LR Clock high - RIGHT */
}
p_i2s_dac[0] <: bitrev(samplesOut[i]); //下一小节：第四部分修改之处。
/* Clock out the LR Clock, the DAC data and Clock in the nextsample into ADC */
doI2SClocks(divide);
} //end for(i=0;i<2;i++)
}
{
/* Do samples transfer */
/* The below looks a bit odd but forces thecompiler to inline twice */
unsigned command;
if(readBuffNo)
command =DoSampleTransfer(c_out, 1, underflowWord);
else
command = DoSampleTransfer(c_out,0, underflowWord);
if(command)
{
return command;
}
/* Reset frame counterand flip the ADC buffer */
frameCount = 0;
readBuffNo = !readBuffNo;
}
四：从ADC获取数据直接发给DAC，实现监听
将上面代码中的这一句：
p_i2s_dac[0] <:bitrev(samplesOut[i]);
改为：
p_i2s_dac[0] <: bitrev(tempsample);//即用收到的数据直接放到I2S
实现监听，但须注意的是切换到听歌状态时，不能听WAV歌曲，可以听DSD，原因是听歌状态的DAC路径被截断了。在正式项目时还需要改变成两种状态可切换。
五：连接android 华为手机
华为手机H60-l01，Android 4.4.2，(1)支持OTG，(2)安装海贝无损音乐播放器，用两个小头的USB连接后可以实现听音乐功能。
