CCS: TMS320F 28335 's ADC module The value that procedure reads and the value that actually measure can have the error inside 100MV, consult how to optimize? The optimization error is within 30mv

Tool/software: Code Composer Studio

initail procedure

#if (CPU_FRQ_150MHZ)     // Default - 150 MHz SYSCLKOUT   use this sysclk
  #define ADC_MODCLK 0x3 // HSPCLK = SYSCLKOUT/2*ADC_MODCLK2 = 150/(2*3)   = 25.0 MHz
#endif
#if (CPU_FRQ_100MHZ)
  #define ADC_MODCLK 0x2 // HSPCLK = SYSCLKOUT/2*ADC_MODCLK2 = 100/(2*2)   = 25.0 MHz
#endif
void Init_ADC(void)
{
 uint16_t tmp = 0;

 EALLOW;
  SysCtrlRegs.HISPCP.all = ADC_MODCLK; // HSPCLK = SYSCLKOUT/ADC_MODCLK
 EDIS;

 AdcRegs.ADCTRL3.all = 0x00E0;   // Power up bandgap/reference/ADC circuits
 tmp = 5000;
 while(tmp--);     // wait for adc stable

 
 AdcRegs.ADCST.all = 0x30;   //first clear int interrupt flag
 AdcRegs.ADCOFFTRIM.all = 0;
 AdcRegs.ADCTRL3.all = 0x0E2;
 //bit7~6:ADCBGRFDN[1:0]:adc 缝隙上电，3上电
 //bit5：ADCPWDN：adc 模块上电，set1 上电
 //bit1~4:ADCCLKPS=1
 // bit0:SMODE_SEL =0  :set 0   顺序采样；   set1 ：同步采样
 // 0 = [ADCCLK = HSPCLK/(CPS+1)], 1 = [ADCCLK = HSPCLK/2*(1)(CPS+1)]; HSPCLK 默认情况下 = CPUSYSCLK/2;
 //ADC module clock = HSPCLK/2*ADC_CKPS   = 25.0MHz/(1*2) = 12.5MHz
//设置为顺序采样模式 0 = 连续采样方式 1 = 并发采样方式
 AdcRegs.ADCTRL1.all = 0x0F50;
 /*bit13~12：SUSMOD=0;
 bit11~8：ACQ_PS =F :16 ADC clocks;
 bit7: CPS =0时钟预分频1
 bit6: CONT_RUN=1；//设置为启停模式 0 = 启停模式，1 = 连续转换模式
 bit5:SEQ_OVRD = 0
 bit4:SEQ_CASC =1//级联模式 0 = 双序列发生器方式， 1 = 级联模式
 */
 //AdcRegs.ADCTRL1.bit.CONT_RUN = 1;

 AdcRegs.ADCTRL2.all = 0x0000;
 AdcRegs.ADCMAXCONV.all = 0x0F;   //最大转换16通道

 AdcRegs.ADCCHSELSEQ1.bit.CONV00 = 0;  // ADCINA0 & ADCINB0
 AdcRegs.ADCCHSELSEQ1.bit.CONV01 = 1;  // ADCINA1 & ADCINB1
 AdcRegs.ADCCHSELSEQ1.bit.CONV02 = 2;  // ADCINA2 & ADCINB2
 AdcRegs.ADCCHSELSEQ1.bit.CONV03 = 3;  // ADCINA3 & ADCINB3

 AdcRegs.ADCCHSELSEQ2.bit.CONV04 = 4;  // ADCINA4 & ADCINB4
 AdcRegs.ADCCHSELSEQ2.bit.CONV05 = 5;  // ADCINA5 & ADCINB5
 AdcRegs.ADCCHSELSEQ2.bit.CONV06 = 6;  // ADCINA6 & ADCINB6
 AdcRegs.ADCCHSELSEQ2.bit.CONV07 = 7;  // ADCINA7 & ADCINB7

 AdcRegs.ADCCHSELSEQ3.bit.CONV08 = 8;  // ADCINA8 & ADCINB8
 AdcRegs.ADCCHSELSEQ3.bit.CONV09 = 9;  // ADCINA9 & ADCINB9
 AdcRegs.ADCCHSELSEQ3.bit.CONV10 = 10;  // ADCINA10 & ADCINB10
 AdcRegs.ADCCHSELSEQ3.bit.CONV11 = 11;  // ADCINA11 & ADCINB11

 AdcRegs.ADCCHSELSEQ4.bit.CONV12 = 12;  // ADCINA12 & ADCINB12
 AdcRegs.ADCCHSELSEQ4.bit.CONV13 = 13;  // ADCINA13 & ADCINB13
 AdcRegs.ADCCHSELSEQ4.bit.CONV14 = 14;  // ADCINA14 & ADCINB14
 AdcRegs.ADCCHSELSEQ4.bit.CONV15 = 15;  // ADCINA15 & ADCINB15
}

read adc result function

void Test_Ai_Handle(Ubyte *paramData)
{
     uint16_t i = 0;
  uint16_t value[16];
  uint16_t chan = 0;
  float tmp = 0;
  uint16_t  delay_tmp = 0;

  chan = paramData[0];
  memset((void *)value, 0, sizeof(value));

  /* handle */
  for(i=0; i<10; i++)//3 change 10
  {
   /* start sw conversion */
   AdcRegs.ADCTRL2.bit.RST_SEQ1 = 1;   // Reset SEQ1
   AdcRegs.ADCTRL2.bit.SOC_SEQ1 = 1;   // sofware start ADC

   /* wait conversion done */
   delay_tmp = 1000;
   while(delay_tmp--);
   while(AdcRegs.ADCST.bit.INT_SEQ1 == 0);

   /* value save */
   value[0] += ((AdcRegs.ADCRESULT0) >> 4);
   value[1] += ((AdcRegs.ADCRESULT1) >> 4);
   value[2] += ((AdcRegs.ADCRESULT2) >> 4);
   value[3] += ((AdcRegs.ADCRESULT3) >> 4);
   value[4] += ((AdcRegs.ADCRESULT4) >> 4);
   value[5] += ((AdcRegs.ADCRESULT5) >> 4);
   value[6] += ((AdcRegs.ADCRESULT6) >> 4);
   value[7] += ((AdcRegs.ADCRESULT7) >> 4);
   value[8] += ((AdcRegs.ADCRESULT8) >> 4);
   value[9] += ((AdcRegs.ADCRESULT9) >> 4);
   value[10] += ((AdcRegs.ADCRESULT10) >> 4);
   value[11] += ((AdcRegs.ADCRESULT11) >> 4);
   value[12] += ((AdcRegs.ADCRESULT12) >> 4);
   value[13] += ((AdcRegs.ADCRESULT13) >> 4);
   value[14] += ((AdcRegs.ADCRESULT14) >> 4);
   value[15] += ((AdcRegs.ADCRESULT15) >> 4);
  }

  tmp = (float)(value[chan-1]) / 10;
  tmp = (3000 * tmp / 4095) ;

  if(tmp >= 1499)
   tmp += 1;
  else;
  paramData[3] = Type_Extrh_U8_Of_U16_TE(tmp);
  paramData[4] = Type_Extrl_U8_Of_U16_TE(tmp);

}