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先说一下情况：
单端测量的时候，即P1.1作为输入的时候，测量是准确的
差分测量的时候，P1.1是AIN+，P1.2是AIN-， P1.1 = 2V，P1.2 = 1V
测量结果mv = 498mv
测量条件：
参考电压是内部参考电压=2.44V，SAR CLOCK = 3MHZ，采用内部时钟=12MHZ
请帮忙看一下程序，是哪里出问题了呢？
主要是看ADC初始化和ADC中断函数
程序如下：
//-----------------------------------------------------------------------------
// Includes
//-----------------------------------------------------------------------------
#include "c8051F340.h" // SFR declarations
#include <stdio.h>
//-----------------------------------------------------------------------------
// 16-bit SFR Definitions for 'F34x
//-----------------------------------------------------------------------------
sfr16 TMR2RL = 0xca; // Timer2 reload value
sfr16 TMR2 = 0xcc; // Timer2 counter
sfr16 ADC0 = 0xbd; // ADC0 result
//-----------------------------------------------------------------------------
// Global CONSTANTS
//-----------------------------------------------------------------------------
#define SYSCLK 12000000 // SYSCLK frequency in Hz
#define BAUDRATE 115200 // Baud rate of UART in bps
sbit LED = P2^2; // LED='1' means ON
//-----------------------------------------------------------------------------
// Function PROTOTYPES
//-----------------------------------------------------------------------------
void SYSCLK_Init (void);
void PORT_Init (void);
void Timer2_Init(void);
void ADC0_Init(void);
void UART0_Init (void);
//-----------------------------------------------------------------------------
// MAIN Routine
//-----------------------------------------------------------------------------
void main (void)
{
PCA0MD &= ~0x40; // WDTE = 0 (clear watchdog timer
// enable)
SYSCLK_Init (); // Initialize system clock to
// 24.5MHz
PORT_Init (); // Initialize crossbar and GPIO
Timer2_Init(); // Init Timer2 to generate
// overflows to trigger ADC
UART0_Init(); // Initialize UART0 for printf's
ADC0_Init(); // Initialize ADC0
EA = 1; // enable global interrupts
while (1) { // spin forever
}
}
//-----------------------------------------------------------------------------
// Initialization Subroutines
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
// SYSCLK_Init
//-----------------------------------------------------------------------------
//
// Return Value: None
// Parameters: None
//
// This routine initializes the system clock to use the internal 12MHz
// oscillator as its clock source. Also enables missing clock detector reset.
//
//-----------------------------------------------------------------------------
void SYSCLK_Init (void)
{
OSCICN = 0x83; // configure internal oscillator for
// 12MHz / 1
RSTSRC = 0x04; // enable missing clock detector
}
//-----------------------------------------------------------------------------
// PORT_Init
//-----------------------------------------------------------------------------
//
// Return Value: None
// Parameters: None
//
// Configure the Crossbar and GPIO ports.
// P0.4 - UART TX (push-pull)
// P0.5 - UART RX
// P1.1 - ADC0 analog input
// P2.2 - LED (push-pull)
//
//-----------------------------------------------------------------------------
void PORT_Init (void)
{
XBR0 = 0x01; // Enable UART0
XBR1 = 0x40; // Enable crossbar and weak pull-ups
P0MDOUT |= 0x10; // Set TX pin to push-pull
P2MDOUT |= 0x04; // enable LED as a push-pull output
P1MDIN &= ~0x06; // set P1.1 as an analog input
P1SKIP &= ~0x06; //datasheet上说要skip
}
//-----------------------------------------------------------------------------
// Timer2_Init
//-----------------------------------------------------------------------------
//
// Return Value: None
// Parameters: None
//
// Configure Timer2 to 16-bit auto-reload and generate an interrupt at 100uS
// intervals. Timer 2 overflow automatically triggers ADC0 conversion.
//
//-----------------------------------------------------------------------------
void Timer2_Init (void)
{
TMR2CN = 0x00; // Stop Timer2; Clear TF2;
// use SYSCLK as timebase, 16-bit
// auto-reload
CKCON |= 0x10; // select SYSCLK for timer 2 source
TMR2RL = 65535 - (SYSCLK / 10000); // init reload value for 100uS
TMR2 = 0xffff; // set to reload immediately
TR2 = 1; // start Timer2
}
//-----------------------------------------------------------------------------
// ADC0_Init
//-----------------------------------------------------------------------------
//
// Return Value: None
// Parameters: None
//
// Configures ADC0 to make single-ended analog measurements on pin P1.1
//
//-----------------------------------------------------------------------------
void ADC0_Init (void)
{
ADC0CN = 0x02; // ADC0 disabled, normal tracking,
// conversion triggered on TMR2 overflow
REF0CN = 0x03; // Enable on-chip VREF and buffer
AMX0P = 0x13; // ADC0 positive input = P1.1
AMX0N = 0x14; // ADC0 negative input = P1.2
// Differential mode
ADC0CF = ((SYSCLK/3000000)-1)<<3; // set SAR clock to 3MHz
ADC0CF &= ~0x04; // right-justify results
EIE1 |= 0x08; // enable ADC0 conversion complete int.
AD0EN = 1; // enable ADC0
}
//-----------------------------------------------------------------------------
// UART0_Init
//-----------------------------------------------------------------------------
//
// Return Value: None
// Parameters: None
//
// Configure the UART0 using Timer1, for <BAUDRATE> and 8-N-1.
//
//-----------------------------------------------------------------------------
void UART0_Init (void)
{
SCON0 = 0x10; // SCON0: 8-bit variable bit rate
// level of STOP bit is ignored
// RX enabled
// ninth bits are zeros
// clear RI0 and TI0 bits
if (SYSCLK/BAUDRATE/2/256 < 1) {
TH1 = -(SYSCLK/BAUDRATE/2);
CKCON |= 0x08; // T1M = 1; SCA1:0 = xx
} else if (SYSCLK/BAUDRATE/2/256 < 4) {
TH1 = -(SYSCLK/BAUDRATE/2/4);
CKCON &= ~0x0B; // T1M = 0; SCA1:0 = 01
CKCON |= 0x01;
} else if (SYSCLK/BAUDRATE/2/256 < 12) {
TH1 = -(SYSCLK/BAUDRATE/2/12);
CKCON &= ~0x0B; // T1M = 0; SCA1:0 = 00
} else if (SYSCLK/BAUDRATE/2/256 < 48) {
TH1 = -(SYSCLK/BAUDRATE/2/48);
CKCON &= ~0x0B; // T1M = 0; SCA1:0 = 10
CKCON |= 0x02;
} else {
while (1); // Error. Unsupported baud rate
}
TL1 = TH1; // init Timer1
TMOD &= ~0xf0; // TMOD: timer 1 in 8-bit autoreload
TMOD |= 0x20;
TR1 = 1; // START Timer1
TI0 = 1; // Indicate TX0 ready
}
//-----------------------------------------------------------------------------
// Interrupt Service Routines
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
// ADC0_ISR
//-----------------------------------------------------------------------------
//
// This ISR averages 2048 samples then prints the result to the terminal. The
// ISR is called after each ADC conversion which is triggered by Timer2.
//
//-----------------------------------------------------------------------------
void ADC0_ISR (void) interrupt 10
{
static long accumulator = 0; // Accumulator for averaging
static unsigned int measurements = 2048; // Measurement counter
unsigned long result=0;
unsigned long mV; // Measured voltage in mV
AD0INT = 0; // Clear ADC0 conv. complete flag
accumulator += ADC0;
measurements--;
if(measurements==0)
{
measurements = 2048;
result = accumulator / 2048;
accumulator=0;
// The 10-bit ADC value is averaged across 2048 measurements.
// The measured voltage applied to P1.4 is then:
//
// Vref (mV)
// measurement (mV) = --------------- * result (bits)
// (2^10)-1 (bits)
mV = result * 2440 / 1023;
printf("P1.1 voltage: %ld mV\n",mV);
}
LED=~LED; // Toggle LED
}
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阿莫论坛20周年了！感谢大家的支持与爱护！！
月入3000的是反美的。收入3万是亲美的。收入30万是移民美国的。收入300万是取得绿卡后回国，教唆那些3000来反美的！
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发表于 2015-3-22 15:41:06
楼主
