TMS320F28335: ADC采样恒定电平但随通道数增加采样数字值也随之增加

chris li

Part Number: TMS320F28335

用28335的ADC进行差分采样时遇到一个问题：我用ADC的A0和B0同时采两路信号如下图的黄色波形和紫色波形

具体是捕获绿色波形的下降沿，进中断触发ADC采样黄色波形和紫色波形8次，ADC采样的配置如下

    EALLOW;
	SysCtrlRegs.PCLKCR0.bit.ADCENCLK = 1;    // ADC
	EDIS;
	// Specific clock setting for this example:
	EALLOW;
	SysCtrlRegs.HISPCP.all = 3;	// HSPCLK = SYSCLKOUT/ADC_MODCLK
	EDIS;
	InitAdc();  // For this example, init the ADC
    AdcRegs.ADCTRL1.bit.ACQ_PS = 0xf;
    AdcRegs.ADCTRL3.bit.ADCCLKPS = 0x1;
    AdcRegs.ADCTRL3.bit.SMODE_SEL = 0x1;     //同步采样模式
    AdcRegs.ADCTRL1.bit.SEQ_CASC = 1;        //双排序器模式
    AdcRegs.ADCMAXCONV.bit.MAX_CONV1 = 0x7;//最大采样通道
    AdcRegs.ADCCHSELSEQ1.bit.CONV00 = 0x0;   //使用A0和B0
    AdcRegs.ADCCHSELSEQ1.bit.CONV01 = 0x0;   //使用A0和B0
    AdcRegs.ADCCHSELSEQ1.bit.CONV02 = 0x0;   //使用A0和B0
    AdcRegs.ADCCHSELSEQ1.bit.CONV03 = 0x0;   //使用A0和B0
    AdcRegs.ADCCHSELSEQ2.bit.CONV04 = 0x0;   //使用A0和B0
    AdcRegs.ADCCHSELSEQ2.bit.CONV05 = 0x0;   //使用A0和B0
    AdcRegs.ADCCHSELSEQ2.bit.CONV06 = 0x0;   //使用A0和B0
    AdcRegs.ADCCHSELSEQ2.bit.CONV07 = 0x0;   //使用A0和B0
    AdcRegs.ADCTRL1.bit.CONT_RUN = 1;       // Setup continuous run

采样结果分别放到了下面的变量里：

    V_OUTDIFFp1 = AdcRegs.ADCRESULT0>>4;
    V_OUTDIFFp2 = AdcRegs.ADCRESULT2>>4;
    V_OUTDIFFp3 = AdcRegs.ADCRESULT4>>4;
    V_OUTDIFFp4 = AdcRegs.ADCRESULT6>>4;
    V_OUTDIFFp5 = AdcRegs.ADCRESULT8>>4;
    V_OUTDIFFp6 = AdcRegs.ADCRESULT10>>4;
    V_OUTDIFFp7 = AdcRegs.ADCRESULT12>>4;
    V_OUTDIFFp8 = AdcRegs.ADCRESULT14>>4;
    V_OUTDIFFn1 = AdcRegs.ADCRESULT1>>4;
    V_OUTDIFFn2 = AdcRegs.ADCRESULT3>>4;
    V_OUTDIFFn3 = AdcRegs.ADCRESULT5>>4;
    V_OUTDIFFn4 = AdcRegs.ADCRESULT7>>4;
    V_OUTDIFFn5 = AdcRegs.ADCRESULT9>>4;
    V_OUTDIFFn6 = AdcRegs.ADCRESULT11>>4;
    V_OUTDIFFn7 = AdcRegs.ADCRESULT13>>4;
    V_OUTDIFFn8 = AdcRegs.ADCRESULT15>>4;

但结果却不一致