您好，
我在学习CSL库中的I2S例程中的CSL_I2S_AudioCodec_DMA例程时，对如下这段配置不明白，程序中ioExpander有什么作用，这段程序在初始化什么？希望大家指导一下，万分感谢！
#ifdef INSTANCE0_I2S
status = ioExpander_Write(0, 2, 0);// SEL_I2C_S0 = 0
status = ioExpander_Write(0, 3, 0);// SEL_I2C_S1 = 0
/* Set AIC_MCBSP_MODE to I2S (disable McBSP) */
status = ioExpander_Write(0, 1, 1);// AIC_MCBSP_MODE = 0
status = ioExpander_Write(0, 2, 0);// SEL_I2C_S0 = 0
status = ioExpander_Write(0, 3, 0);// SEL_I2C_S1 = 0
/* Set AIC_MCBSP_MODE to I2S (disable McBSP) */
status = ioExpander_Write(0, 1, 1);// AIC_MCBSP_MODE = 0
status = ioExpander_Write(1, 0, 1); /* Enable SEL_MMC0_I2S */
/* Release AIC3204 reset */
status = ioExpander_Write(0, 0, 0);// AIC_RST = 0
if (status != CSL_SOK)
{
printf("ERROR: ioExpander_Write Failed\n");
exit(EXIT_FAILURE);
}
#else
/* Release AIC3204 reset */
status = ioExpander_Write(0, 0, 0);// AIC_RST = 0
if (status != CSL_SOK)
{
printf("ERROR: ioExpander_Write Failed\n");
exit(EXIT_FAILURE);
}
#else
