fet430_oa1_inverting-pga.c

msp430开发c语言例程

//******************************************************************************
//   MSP-FET430P430 Demo - OA1 Configured For Inverting PGA Mode
//
//   Description; Configure OA1 of the MSP430FG439 for Inverting PGA mode.
//   In this mode, the + terminal must be supplied with an offset, since the OA
//   is a single-supply opamp, and the input must be positive. If an offset is
//   not supplied, the opamp will try to drive its output negative, which
//   cannot be done. In this example, the offset is provided by DAC0 and is 1.5V.
//   The - terminal is connected to the R ladder tap and the OAFBRx bits select
//   the gain. The input signal should be AC coupled.
//   //* MSP430FG439 Device Required*//
// 
//                MSP430FG439   
//             -------------------
//         /|\|                XIN|-  
//          | |                   |
//          --|RST            XOUT|-
//            |                   |
//            |      P6.4/A4/OA1I0|---||--< Input
//            |       P6.3/A3/OA1O|->  OA1 Inverted, Amplified, Offset Output
//            |                   |
//
//   M.Mitchell
//   Texas Instruments, Inc
//   April 2004
//   Built with IAR Embedded Workbench Version: 2.21B
//******************************************************************************

#include  <msp430xG43x.h>

void main(void)
{
  WDTCTL = WDTPW + WDTHOLD;             // Stop watchdog timer
  ADC12CTL0 = REFON + REF2_5V;          // Reference = 2.5V for DAC0
  DAC12_0CTL = DAC12IR + DAC12AMP_2 + DAC12ENC;
  DAC12_0DAT = 0x099A;                  // Offset level = 1.5V
  
  OA1CTL0 = OAP_2+OAPM_1+OAADC1;        // Select inputs, power mode
  OA1CTL1 = OAFC_6+OAFBR_6 + OARRIP;    // Mode, OAFBRx sets gain
  
  LPM3;
}