使用RT1011 使用MQS端口播放音频有轻微的“呼呼”声音，音频源是16kbps，16位，单通道，wav格式音频。音频源音量大时很难听清噪音，音频源声音很小时 就很容易听清。
改变输入的电阻和电容，原本的音频过滤掉了，也可以很清楚的听到“呼呼”的噪音
mqs电路图
mqs参数
/* Select Audio PLL (786.432 MHz) as sai1 clock source */
#define MQS_SAI_CLOCK_SOURCE_SELECT (2U)
/* Clock pre divider for sai clock source */
#define MQS_SAI_CLOCK_SOURCE_PRE_DIVIDER (3U)
/* Clock divider for sai clock source */
#define MQS_SAI_CLOCK_SOURCE_DIVIDER (4U)
/* Get frequency of sai clock: SAI3_Clock = 786.48MHz /(1+0)/(63+1) = 12.14MHz */
/* Get frequency of sai clock: SAI3_Clock = 786.48MHz /(3+1)/(4+1) = 39.3MHz */
#define MQS_SAI_CLK_FREQ (CLOCK_GetFreq(kCLOCK_AudioPllClk) / (MQS_SAI_CLOCK_SOURCE_DIVIDER + 1U) / (MQS_SAI_CLOCK_SOURCE_PRE_DIVIDER + 1U))
void configMQS(void)
{
CCM->CCGR0 = CCM->CCGR0 & (~CCM_CCGR0_CG2_MASK) | CCM_CCGR0_CG2(3); /* Enable MQS hmclk. */
//CLOCK_EnableClock(kCLOCK_Mqs);
IOMUXC_MQSEnterSoftwareReset(IOMUXC_GPR, true); /* Reset MQS. */
IOMUXC_MQSEnterSoftwareReset(IOMUXC_GPR, false); /* Release reset MQS. */
IOMUXC_MQSEnable(IOMUXC_GPR, true); /* Enable MQS. */
IOMUXC_MQSConfig(IOMUXC_GPR, kIOMUXC_MqsPwmOverSampleRate64, 1); /* 39.321MHz/64/(1+1) = 0.3MHz
12.14Mhz/32/(0+1)
Higher frequency PWM involves less low frequency harmonic.*/
}
