msp430 adc12 关于参考电压的问题

只看该作者 · 2013-8-26 22:00

对参考电压的选择有很多疑问，比如下面这个例子我在很多地方都看到过 void main（void）
{
      WDTCTL = WDTPW+WDTHOLD;
      ADC12CTL0 = ADC12ON+SHT0_8+MSC;
      ADC12CTL1 = SHP+CONSEQ_2;
      ADC12IE = 0x01;
      ADC12CTL0 |= ENC;
      ADC12CTL0 |= ADC12SC;

}
在上面的这段代码里，我不知道他到底是怎么设置参考电压的
在ADC12CTL0寄存器中，有一个REF2_5V,和REFON,说是选择内部参考电压的就是2.5V和1.5V
但是在ADC2MCTLx寄存器中SREF 又有6中情况，应该是选择外部参考电压的把，

那在上面这个程序中，如何知道VR+和VR-呢，怎么计算测量的电压

还有就是我想用内部参考电压，测量430内部的温度传感器的温度，一下的初始化设置对不对啊
ADC12CTL0=ADC12ON+SHT0_15+MSC+REF2_5V;
ADC12CTL1=SHP+CONSEQ_2;
ADC12MCTL0=INCH_10;
ADC12IE=0x01;
ADC12CTL0|=ENC;
ADC12CTL0|=ADC12SC;

只看该作者 · 2013-8-26 22:07

Setting REFON=1 enables the internal reference. When REF2_5V = 1, the internal reference is 2.5 V, the
reference is 1.5 V when REF2_5V = 0.
REFON=1时，如果REF2_5V=0，那么内部参考电压为1.5V,REF2_5V=1时内部参考电压为2.5V
选择外部参考电压通过SREFx，从datasheet里可以看到有很多种选择，Vref这种是内部参考电压，Veref这种是外部参考电压。

下面是一个内部温度传感器的测量程序

//******************************************************************************
//  MSP430G2x33/G2x53 Demo - ADC10, Sample A10 Temp and Convert to oC and oF
//
//  Description: A single sample is made on A10 with reference to internal
//  1.5V Vref. Software sets ADC10SC to start sample and conversion - ADC10SC
//  automatically cleared at EOC. ADC10 internal oscillator/4 times sample
//  (64x) and conversion. In Mainloop MSP430 waits in LPM0 to save power until
//  ADC10 conversion complete, ADC10_ISR will force exit from any LPMx in
//  Mainloop on reti. Temperaure in oC stored in IntDegC, oF in IntDegF.
//  Uncalibrated temperature measured from device to device will vary with
//  slope and offset - please see datasheet.
//  ACLK = n/a, MCLK = SMCLK = default DCO ~1.2MHz, ADC10CLK = ADC10OSC/4
//
//             MSP430G2x33/G2x53
//          -----------------
//       /|\|             XIN|-
//       | |                |
//       --|RST       XOUT|-
//          |                |
//          |A10             |
//
//  D. Dang
//  Texas Instruments Inc.
//  December 2010
// Built with CCS Version 4.2.0 and IAR Embedded Workbench Version: 5.10
//******************************************************************************
#include  "msp430g2553.h"

long temp;
long IntDegF;
long IntDegC;

void main(void)
{
  WDTCTL = WDTPW + WDTHOLD;                // Stop WDT
  ADC10CTL1 = INCH_10 + ADC10DIV_3;       // Temp Sensor ADC10CLK/4
  ADC10CTL0 = SREF_1 + ADC10SHT_3 + REFON + ADC10ON + ADC10IE;
  __enable_interrupt();                   // Enable interrupts.
  TACCR0 = 30;                            // Delay to allow Ref to settle
  TACCTL0 |= CCIE;                         // Compare-mode interrupt.
  TACTL = TASSEL_2 | MC_1;                // TACLK = SMCLK, Up mode.
  LPM0;                                  // Wait for delay.
  TACCTL0 &= ~CCIE;                      // Disable timer Interrupt
  __disable_interrupt();

  while(1)
  {
ADC10CTL0 |= ENC + ADC10SC;          // Sampling and conversion start
__bis_SR_register(CPUOFF + GIE);       // LPM0 with interrupts enabled

// oF = ((A10/1024)*1500mV)-923mV)*1/1.97mV = A10*761/1024 - 468
temp = ADC10MEM;
IntDegF = ((temp - 630) * 761) / 1024;

// oC = ((A10/1024)*1500mV)-986mV)*1/3.55mV = A10*423/1024 - 278
temp = ADC10MEM;
IntDegC = ((temp - 673) * 423) / 1024;

__no_operation();                      // SET BREAKPOINT HERE
  }
}

// ADC10 interrupt service routine
#pragma vector=ADC10_VECTOR
__interrupt void ADC10_ISR (void)
{
  __bic_SR_register_on_exit(CPUOFF);       // Clear CPUOFF bit from 0(SR)
}

#pragma vector=TIMER0_A0_VECTOR
__interrupt void ta0_isr(void)
{
  TACTL = 0;
  LPM0_EXIT;                               // Exit LPM0 on return
}