[资料分享] Ti的C28x系列的ADC经验

Jacktang 2019-9-17 20:35 楼主

笔者使用过的项目中，使用的ADC都是DSP的片内ADC，使用片内ADC的好处是，转换速度快，节约成本，这是相比片外ADC的优势。

DSP_28069的ADC精度是12位，DSP_28377D的ADC精度可以选择为12位，也可以选择为16位，笔者这里采用的是12位，两种DSP的采样模式都是单端模式。

DSP的ADC采样精度和参考电压有很大的关系，一般选择外部参考电压，参考电压一定要加RC滤波电路。

计算公式如下：

关于ADC其他方面的原理，这里就不作介绍了，如果读者想了解更多，可以搜搜其他博客看看。

笔者在项目中使用ADC，基本上只涉及以下几个方面：

ADC的初始化

ADC初始化，主要分为两个部分，ADC的模式选择，（精度模式、采样方式（差分或单端）），中断触发时刻，使能中断等。

void InitAdcPart1(void)
{

   EALLOW;
   SysCtrlRegs.PCLKCR0.bit.ADCENCLK = 1;
   (*Device_cal)();
   EDIS;

   EALLOW;
   AdcRegs.ADCCTL1.bit.ADCBGPWD = 1; // Power ADC BG
   AdcRegs.ADCCTL1.bit.ADCREFPWD = 1; // Power reference
   AdcRegs.ADCCTL1.bit.ADCPWDN = 1; // Power ADC
   AdcRegs.ADCCTL1.bit.ADCENABLE = 1; // Enable ADC
   AdcRegs.ADCCTL1.bit.ADCREFSEL = 1; // External VREFHI or VREFLO pins used for
//reference generation
EDIS;

DELAY_US(1000L); // Delay before converting ADC channels

EALLOW;
AdcRegs.ADCCTL2.bit.CLKDIV2EN = 0; //ADCCLK = SYSCLK = 80Mhz
EDIS;

DELAY_US(1000L); // Delay before converting ADC channels
}

void InitAdcPart2(void)
{
   EALLOW;
   AdcRegs.ADCCTL2.bit.ADCNONOVERLAP = 1;   // Overlap of sample is not allowed
   AdcRegs.ADCSAMPLEMODE.all = 0; // Single sample mode

//物理采样通道选择
   AdcRegs.ADCSOC0CTL.bit.CHSEL = 0; //ADCINA0
   AdcRegs.ADCSOC1CTL.bit.CHSEL = 1;
   AdcRegs.ADCSOC2CTL.bit.CHSEL = 2;
   AdcRegs.ADCSOC3CTL.bit.CHSEL = 3;
   AdcRegs.ADCSOC4CTL.bit.CHSEL = 4;
   AdcRegs.ADCSOC5CTL.bit.CHSEL = 5;
   AdcRegs.ADCSOC6CTL.bit.CHSEL = 6;
   AdcRegs.ADCSOC7CTL.bit.CHSEL = 7; //ADCINA7
   AdcRegs.ADCSOC8CTL.bit.CHSEL = 8; //ADCINB0
   AdcRegs.ADCSOC9CTL.bit.CHSEL = 9;
   AdcRegs.ADCSOC10CTL.bit.CHSEL= 10;
   AdcRegs.ADCSOC11CTL.bit.CHSEL= 11;
   AdcRegs.ADCSOC12CTL.bit.CHSEL= 12;
   AdcRegs.ADCSOC13CTL.bit.CHSEL= 13;
   AdcRegs.ADCSOC14CTL.bit.CHSEL= 14;
   AdcRegs.ADCSOC15CTL.bit.CHSEL= 15; //ADCINB7

//采样保持时间
//Sample window =(19 + 1 clock cycles).
   AdcRegs.ADCSOC0CTL.bit.ACQPS = 19;
   AdcRegs.ADCSOC1CTL.bit.ACQPS = 19;
   AdcRegs.ADCSOC2CTL.bit.ACQPS = 19;
   AdcRegs.ADCSOC3CTL.bit.ACQPS = 19;
   AdcRegs.ADCSOC4CTL.bit.ACQPS = 19;
   AdcRegs.ADCSOC5CTL.bit.ACQPS = 19;
   AdcRegs.ADCSOC6CTL.bit.ACQPS = 19;
   AdcRegs.ADCSOC7CTL.bit.ACQPS = 19;
   AdcRegs.ADCSOC8CTL.bit.ACQPS = 19;
   AdcRegs.ADCSOC9CTL.bit.ACQPS = 19;
   AdcRegs.ADCSOC10CTL.bit.ACQPS = 19;
   AdcRegs.ADCSOC11CTL.bit.ACQPS = 19;
   AdcRegs.ADCSOC12CTL.bit.ACQPS = 19;
   AdcRegs.ADCSOC13CTL.bit.ACQPS = 19;
   AdcRegs.ADCSOC14CTL.bit.ACQPS = 19;
   AdcRegs.ADCSOC15CTL.bit.ACQPS = 19;

//ADC触发源
   //4//set SOC0 start trigger on XIN2
   AdcRegs.ADCSOC0CTL.bit.TRIGSEL = 4; //4;// // 5 set SOC0 start trigger on EPWM1A
   AdcRegs.ADCSOC1CTL.bit.TRIGSEL = 4; //4;
   AdcRegs.ADCSOC2CTL.bit.TRIGSEL = 4; //4;
   AdcRegs.ADCSOC3CTL.bit.TRIGSEL = 4; //4;
   AdcRegs.ADCSOC4CTL.bit.TRIGSEL = 4; //4;
   AdcRegs.ADCSOC5CTL.bit.TRIGSEL = 4; //4;
   AdcRegs.ADCSOC6CTL.bit.TRIGSEL = 4; //4;
   AdcRegs.ADCSOC7CTL.bit.TRIGSEL = 4; //4;
   AdcRegs.ADCSOC8CTL.bit.TRIGSEL = 4; //4;
   AdcRegs.ADCSOC9CTL.bit.TRIGSEL = 4; //4;
   AdcRegs.ADCSOC10CTL.bit.TRIGSEL = 4; //4;
   AdcRegs.ADCSOC11CTL.bit.TRIGSEL = 4; //4;
   AdcRegs.ADCSOC12CTL.bit.TRIGSEL = 4; //4;
   AdcRegs.ADCSOC13CTL.bit.TRIGSEL = 4; //4;
   AdcRegs.ADCSOC14CTL.bit.TRIGSEL = 4; //4;
   AdcRegs.ADCSOC15CTL.bit.TRIGSEL = 4; //4;

   EDIS;
}
void InitAdcINT(void)
{
   EALLOW;
   AdcRegs.ADCCTL1.bit.INTPULSEPOS   = 1;   // ADCINT1 trips after AdcResults latch
   AdcRegs.INTSEL1N2.bit.INT1CONT = 0;   // Disable ADCINT1 Continuous mode
   AdcRegs.INTSEL1N2.bit.INT1SEL    = 15; // EOC15 is trigger for ADCINT1
   EALLOW;
}
void EnableAdcInterrupt(void)
{
   EALLOW;
   AdcRegs.INTSEL1N2.bit.INT1E = 1;   // Enabled ADCINT1
   EDIS;
}
ADC的触发源，即表示如何启动ADC转换，一般用PWM启动ADC，或者外部GPIO启动ADC，比如FPGA外部触发ADC。

ADC转换的结果ADCRESULT

ADCRESULT表示数据采集的源头，各种电压电流，都是通过这个公式（ADCRESULT - 零漂）* 系数而得到的。

ADC的转换完成后触发的中断

ADC触发的中断，一般是整个DSP系统中的主中断，这个中断里会运行一些数据采集、算法、故障保护等实时性要求比较高的函数。

void InitInterrupt(void)
{

   EALLOW; // This is needed to write to EALLOW protected register
   PieVectTable.ADCINT1 = &Interrupt_Adc1;
   EDIS; // This is needed to disable write to EALLOW protected registers
   PieCtrlRegs.PIEIFR1.bit.INTx1 = 0;
   PieCtrlRegs.PIEIER1.bit.INTx1 = 1;   // Enable ADC1 INT 1.1 in the PIE
   PieCtrlRegs.PIEACK.all = 0x0FFF;       //set all ack to 0
}
__interrupt void Interrupt_Adc1(void)
{
ServeMainInt();
AdcRegs.ADCINTFLGCLR.bit.ADCINT1 = 1;   //Clear ADCINT1 flag reinitialize
//for next SOC
PieCtrlRegs.PIEACK.all |= PIEACK_GROUP1; // Acknowledge interrupt to PIE
}