MSP430F5529学习笔记2-ADC12

只看该作者 · 2016-9-26 22:00

开发版型号：SEED—MSP430F5529A
开发工具：CCS 5.4v
以下内容是CCS中ADC12操作的一些简单的demo，现整理如下：
有关MSP430F5529芯片ADC12相关资料，可参考《MSP430x5xx and MSP430x6xx Family User's Guide (Rev. M)——Chapter 28 ADC12_A》
1：demo描述
Description: A single sample is made on A0 with reference to AVcc.

Software sets ADC12SC to start sample and conversion - ADC12SC

automatically cleared at EOC. ADC12 internal oscillator times sample (16x)

and conversion. In Mainloop MSP430 waits in LPM0 to save power until ADC12

conversion complete, ADC12_ISR will force exit from LPM0 in Mainloop on

reti. If A0 > 0.5*AVcc, P1.0 set, else reset.

参考AVcc电压、以A0定时器作为采样输入信号源的、单通道单次模式采样，当采样信号大于0.5*AVcc时，P1.0置位，否则为0。
代码如下：
#include <msp430.h>

int main(void)
{
  WDTCTL = WDTPW + WDTHOLD;                // Stop WDT
  ADC12CTL0 = ADC12SHT02 + ADC12ON;       // Sampling time, ADC12 on
  ADC12CTL1 = ADC12SHP;                   // Use sampling timer
  ADC12IE = 0x01;                         // Enable interrupt
  ADC12CTL0 |= ADC12ENC;
  P6SEL |= 0x01;                         // P6.0 ADC option select
  P1DIR |= 0x01;                         // P1.0 output

  while (1)
  {
ADC12CTL0 |= ADC12SC;                // Start sampling/conversion

__bis_SR_register(LPM0_bits + GIE);    // LPM0, ADC12_ISR will force exit
__no_operation();                      // For debugger
  }
}

#pragma vector = ADC12_VECTOR
__interrupt void ADC12_ISR(void)
{
  switch(__even_in_range(ADC12IV,34))
  {
  case  0: break;                         // Vector  0:  No interrupt
  case  2: break;                         // Vector  2:  ADC overflow
  case  4: break;                         // Vector  4:  ADC timing overflow
  case  6:                               // Vector  6:  ADC12IFG0
if (ADC12MEM0 >= 0x7ff)                // ADC12MEM = A0 > 0.5AVcc?
   P1OUT |= BIT0;                      // P1.0 = 1
else
   P1OUT &= ~BIT0;                      // P1.0 = 0

__bic_SR_register_on_exit(LPM0_bits); // Exit active CPU
  case  8: break;                         // Vector  8:  ADC12IFG1
  case 10: break;                         // Vector 10:  ADC12IFG2
  case 12: break;                         // Vector 12:  ADC12IFG3
  case 14: break;                         // Vector 14:  ADC12IFG4
  case 16: break;                         // Vector 16:  ADC12IFG5
  case 18: break;                         // Vector 18:  ADC12IFG6
  case 20: break;                         // Vector 20:  ADC12IFG7
  case 22: break;                         // Vector 22:  ADC12IFG8
  case 24: break;                         // Vector 24:  ADC12IFG9
  case 26: break;                         // Vector 26:  ADC12IFG10
  case 28: break;                         // Vector 28:  ADC12IFG11
  case 30: break;                         // Vector 30:  ADC12IFG12
  case 32: break;                         // Vector 32:  ADC12IFG13
  case 34: break;                         // Vector 34:  ADC12IFG14
  default: break;
  }
}
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2：代码分析
1）主函数中代码：
ADC12CTL0 = ADC12SHT02 + ADC12ON;       // Sampling time, ADC12 on
ADC12CTL1 = ADC12SHP;                   // Use sampling timer
ADC12IE = 0x01;                         // Enable interrupt
ADC12CTL0 |= ADC12ENC;

ADC12CTL0 |= ADC12SC;                // Start sampling/conversion
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参考控制寄存器如下：

ADCSHT0x :采样保持定时器0,该四位定义了保存在转换存储寄存器中转换结果的采样周期；
ADC12ENC：转换允许
ADC12SHP：选择采样定时器A0输出
ADC12IE：中断允许 (来自中断允许寄存器)

2）中断部分代码：
中断寄存向量ADC12IV中的数字（0-36）用来判断中断标志寄存器中相关位是否置位，此时表明转换结果已经装入转换存储寄存器中，具体数字的含义参见下图：

3）
if (ADC12MEM0 >= 0x7ff)                // ADC12MEM = A0 > 0.5AVcc?
P1OUT |= BIT0;                      // P1.0 = 1
else
P1OUT &= ~BIT0;                      // P1.0 = 0
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参考电压使用VCC，因为ADC精度为12位（4095），所以0x7FF（2047）就是0.5Vcc的AD值