【DSP】TMS320F28335的ADC模块

一、功能说明

• 12位内建采样保持的模数转换器
• 模拟输入电平：0~3V
• 16个转换通道
• 最快转换时钟频率12.5MHz（奈奎斯特定则，25MHz最高能采样12.5MHz的信号）
• 多触发源：软件、ePWM和GPIO
• 两种采样模式：级联和双通道模式

软件设置流程

//1.ADC时钟使能
SysCtrlRegs.PCLKCR0.bit.ADCENCLK = 1;//在InitSysCtrl()函数里
//2.时钟分频
EALLOW;
SysCtrlRegs.HISPCP.all = 0x3;//HSPCLK = SYSCLKOUT/2*HISPCP = 150/(2*3)   = 25.0 MHz
ADC_cal();
EDIS;
AdcRegs.ADCTRL3.all = 0x00E0;  // Power up bandgap/reference/ADC circuits
DELAY_US(ADC_usDELAY);         // Delay before converting ADC channels
AdcRegs.ADCTRL3.bit.ADCCLKPS = 0x0;//Fclk = HSPCLK/(2*ADCCLKPS),但当ADCCLKPS=0时，Fclk = HSPCLK
AdcRegs.ADCTRL1.bit.CPS = 0x0;//ADCCLK = Fclk / (CPS+1)
//3.通道设置
//4.触发源设置
//5.中断源设置

二、模式说明

2.1 级联模式

//3.通道设置
AdcRegs.ADCTRL1.bit.SEQ_CASC = 0x1;//0-dual, 1-Cascaded
AdcRegs.ADCMAXCONV.all = 0x000F;       // Setup 16 conv's on SEQ
AdcRegs.ADCCHSELSEQ1.bit.CONV00 = 0x0; // Setup ADCINA0 as 1st SEQ conv.
AdcRegs.ADCCHSELSEQ1.bit.CONV01 = 0x1; // Setup ADCINA1 as 2nd SEQ conv.
AdcRegs.ADCCHSELSEQ1.bit.CONV02 = 0x2; // Setup ADCINA2 as 3rd SEQ conv.
AdcRegs.ADCCHSELSEQ1.bit.CONV03 = 0x3; // Setup ADCINA3 as 4th SEQ conv.
AdcRegs.ADCCHSELSEQ2.bit.CONV04 = 0x4; // Setup ADCINA4 as 5th SEQ conv.
AdcRegs.ADCCHSELSEQ2.bit.CONV05 = 0x5; // Setup ADCINA5 as 6th SEQ conv.
AdcRegs.ADCCHSELSEQ2.bit.CONV06 = 0x6; // Setup ADCINA6 as 7th SEQ conv.
AdcRegs.ADCCHSELSEQ2.bit.CONV07 = 0x7; // Setup ADCINA7 as 8th SEQ conv.
AdcRegs.ADCCHSELSEQ3.bit.CONV08 = 0x8; // Setup ADCINB0 as 9th SEQ conv.
AdcRegs.ADCCHSELSEQ3.bit.CONV09 = 0x9; // Setup ADCINB1 as 10th SEQ conv.
AdcRegs.ADCCHSELSEQ3.bit.CONV10 = 0xA; // Setup ADCINB2 as 11th SEQ conv.
AdcRegs.ADCCHSELSEQ3.bit.CONV11 = 0xB; // Setup ADCINB3 as 12th SEQ conv.
AdcRegs.ADCCHSELSEQ4.bit.CONV12 = 0xC; // Setup ADCINB4 as 13th SEQ conv.
AdcRegs.ADCCHSELSEQ4.bit.CONV13 = 0xD; // Setup ADCINB5 as 14th SEQ conv.
AdcRegs.ADCCHSELSEQ4.bit.CONV14 = 0xE; // Setup ADCINB6 as 15th SEQ conv.
AdcRegs.ADCCHSELSEQ4.bit.CONV15 = 0xF; // Setup ADCINB7 as 16th SEQ conv.

2.2 双通道模式

//3.通道设置
AdcRegs.ADCTRL1.bit.SEQ_CASC = 0x0;//0-dual, 1-Cascaded
AdcRegs.ADCMAXCONV.all = 0x0077;       // Setup 8 conv's on SEQ1 and 8 conv's on SEQ2
AdcRegs.ADCCHSELSEQ1.bit.CONV00 = 0x0; // Setup ADCINA0 as 1st SEQ1 conv.
AdcRegs.ADCCHSELSEQ1.bit.CONV01 = 0x1; // Setup ADCINA1 as 2nd SEQ1 conv.
AdcRegs.ADCCHSELSEQ1.bit.CONV02 = 0x2; // Setup ADCINA2 as 3rd SEQ1 conv.
AdcRegs.ADCCHSELSEQ1.bit.CONV03 = 0x3; // Setup ADCINA3 as 4th SEQ1 conv.
AdcRegs.ADCCHSELSEQ2.bit.CONV04 = 0x4; // Setup ADCINA4 as 5th SEQ1 conv.
AdcRegs.ADCCHSELSEQ2.bit.CONV05 = 0x5; // Setup ADCINA5 as 6th SEQ1 conv.
AdcRegs.ADCCHSELSEQ2.bit.CONV06 = 0x6; // Setup ADCINA6 as 7th SEQ1 conv.
AdcRegs.ADCCHSELSEQ2.bit.CONV07 = 0x7; // Setup ADCINA7 as 8th SEQ1 conv.
AdcRegs.ADCCHSELSEQ3.bit.CONV08 = 0x8; // Setup ADCINB0 as 1st SEQ2 conv.
AdcRegs.ADCCHSELSEQ3.bit.CONV09 = 0x9; // Setup ADCINB1 as 2nd SEQ2 conv.
AdcRegs.ADCCHSELSEQ3.bit.CONV10 = 0xA; // Setup ADCINB2 as 3rd SEQ2 conv.
AdcRegs.ADCCHSELSEQ3.bit.CONV11 = 0xB; // Setup ADCINB3 as 4th SEQ2 conv.
AdcRegs.ADCCHSELSEQ4.bit.CONV12 = 0xC; // Setup ADCINB4 as 5th SEQ2 conv.
AdcRegs.ADCCHSELSEQ4.bit.CONV13 = 0xD; // Setup ADCINB5 as 6th SEQ2 conv.
AdcRegs.ADCCHSELSEQ4.bit.CONV14 = 0xE; // Setup ADCINB6 as 7th SEQ2 conv.
AdcRegs.ADCCHSELSEQ4.bit.CONV15 = 0xF; // Setup ADCINB7 as 8th SEQ2 conv.

三、触发源

//4.触发源设置
AdcRegs.ADCTRL2.bit.SOC_SEQ1 = 1;//软触发（用于级联、双通道1#）
AdcRegs.ADCTRL2.bit.SOC_SEQ2 = 1;//软触发（用于双通道2#）
AdcRegs.ADCTRL2.bit.EPWM_SOCA_SEQ1 = 1;//ePWM触发（用于双通道1#）
AdcRegs.ADCTRL2.bit.EPWM_SOCB_SEQ2 = 1;//ePWM触发（用于双通道2#）
AdcRegs.ADCTRL2.bit.EPWM_SOCB_SEQ = 1;//ePWM触发（用于级联）

四、中断源

//5.中断源设置
AdcRegs.ADCTRL2.bit.INT_ENA_SEQ1 = 1; //用于级联、双通道1#
AdcRegs.ADCTRL2.bit.INT_ENA_SEQ2 = 1; //双通道2#

五、接收转换结果

5.1 中断式

/*
 * AD的外部中断程序【中等优先级】
 * 中断触发信号：EPWM
*/
interrupt void ADC_ISR(void)
{
  Voltage[0] = AdcRegs.ADCRESULT0 >>4;
  Voltage[1] = AdcRegs.ADCRESULT1 >>4;
  Voltage[2] = AdcRegs.ADCRESULT2 >>4;
  Voltage[3] = AdcRegs.ADCRESULT3 >>4;
  Voltage[4] = AdcRegs.ADCRESULT4 >>4;
  Voltage[5] = AdcRegs.ADCRESULT5 >>4;
  Voltage[6] = AdcRegs.ADCRESULT6 >>4;
  Voltage[7] = AdcRegs.ADCRESULT7 >>4;
  Voltage[8] = AdcRegs.ADCRESULT8 >>4;
  Voltage[9] = AdcRegs.ADCRESULT9 >>4;
  Voltage[10] = AdcRegs.ADCRESULT10 >>4;
  Voltage[11] = AdcRegs.ADCRESULT11 >>4;
  Voltage[12] = AdcRegs.ADCRESULT12 >>4;
  Voltage[13] = AdcRegs.ADCRESULT13 >>4;
  Voltage[14] = AdcRegs.ADCRESULT14 >>4;
  Voltage[15] = AdcRegs.ADCRESULT15 >>4;

  // Reinitialize for next ADC sequence
  AdcRegs.ADCTRL2.bit.RST_SEQ1 = 1;         // Reset SEQ1
  AdcRegs.ADCST.bit.INT_SEQ1_CLR = 1;       // Clear INT SEQ1 bit
  PieCtrlRegs.PIEACK.all = PIEACK_GROUP1;   // Acknowledge interrupt to PIE
  
  return;
}

5.2 查询式

while(AdcRegs.ADCST.bit.INT_SEQ1 == 0);
test[0] = AdcRegs.ADCRESULT0 >>4;
test[1] = AdcRegs.ADCRESULT1 >>4;
test[2] = AdcRegs.ADCRESULT2 >>4;
test[3] = AdcRegs.ADCRESULT3 >>4;
test[4] = AdcRegs.ADCRESULT4 >>4;
test[5] = AdcRegs.ADCRESULT5 >>4;
test[6] = AdcRegs.ADCRESULT6 >>4;
test[7] = AdcRegs.ADCRESULT7 >>4;
test[8] = AdcRegs.ADCRESULT8 >>4;
test[9] = AdcRegs.ADCRESULT9 >>4;
test[10] = AdcRegs.ADCRESULT10 >>4;
test[11] = AdcRegs.ADCRESULT11 >>4;
test[12] = AdcRegs.ADCRESULT12 >>4;
test[13] = AdcRegs.ADCRESULT13 >>4;
test[14] = AdcRegs.ADCRESULT14 >>4;
test[15] = AdcRegs.ADCRESULT15 >>4;
AdcRegs.ADCTRL2.bit.RST_SEQ1 = 1;// Reset SEQ1
AdcRegs.ADCST.bit.INT_SEQ1_CLR = 1;

六、其他设置

6.1 运行模式
运行模式分为start-stop和continuous两种模式，通过以下代码配置：

AdcRegs.ADCTRL1.bit.CONT_RUN = 0x0; //0-start stop mode; 1-Continuous conversion mode

start-stop模式下，AD转换结束后等待触发信号，才开始进行下一次的AD转换；
continuous模式下，AD转换结束后无需等待触发信号，立即开始下一次的AD转换。
6.2 SOC脉宽设置

AdcRegs.ADCTRL1.bit.ACQ_PS = 0xF;//Acquisition window size

SOC脉宽是（ACQ_PS + 1）倍的ADCLK周期。
6.3 复位启动

AdcRegs.ADCTRL1.bit.SEQ_OVRD = 0x0;

仅用在continuous模式里面，如果该位为0，则新的SOC来时从复位状态启动，如SEQ1和级联模式下，重新从CONV00开始；如果该位为1，则不会从复位状态开始，直接从现在的转换序列开始，直到最后停止。

七、疑问

1. 什么时候触发中断？
   答：当SEQ_CNTR = 0时，INT_SEQ = 1，且产生中断。否则，INT_SEQ = 0。

2. ePWM触发双通道ADC，只能转换一个通道，什么原因？
   答：ACQ_PS的值太大，改小后，触发脉冲变小，可实现双通道。