同时多通道ADC配置中CH0的低值错误

大家好，正如标题所说的，我配置了dSPIC33 FJ256GP710A的ADC1，用于同时多通道模式，但是我得到了CH0的错误值。在四个通道中，我有以下类似的输入：CH0+＝AN3CH0-＝VREF CH123+= AN0，AN1，AN2CH123-＝VREF，现在，我做了一个残忍的事。测试：通过Pad Drand板将AN3、AN0和AN1连接到GND和AN2到+3.3V……我的测试程序通过UART将四个通道的数据发送到matlab，结果是在列上具有通道的值矩阵，并且泛型行是：[68, 1, 2，1023 ]现在，CH3有一个很好的值，同样是CH1和CH2（尽管有噪声），但是CH0有一个不可接受的值……也改变了CH0的模拟输入，我得到了类似的值，但是我从来没有得到接近零的值……有人知道我做错了什么吗？提前感谢您的帮助！下面是我的代码：全局变量



      以下为原文

    Hi everyone,
as the title says, I configured the ADC1 of the dspic33fj256gp710a for working in simultaneous multi-channel mode, but I obtain wrong values for CH0.

On the four channels I have the followings analogic inputs:
CH0+ = AN3
CH0- = Vref-
CH123+ = AN0, AN1, AN2
CH123- = Vref-

Now, I made a brutal test: through a pictail doughter board I linked AN3, AN0 and AN1 to GND and AN2 to +3.3V...
My test program sends the data of the four channels to matlab through the UART, and the result is a matrix of values that has the channels on the columns, and the generic row is:
[ 68, 1, 2, 1023 ]

Now, CH3 has a good value, and so also CH1 and CH2 (in spite of the noise), but CH0 has an unacceptable value...
Also changing the analogic input for CH0, I get similar values, but I never obtain values near to zero...

Have someone idea of what I'm doing wrong?
Thank you in advance for your help!

In the following there is my code:

• Global variables
  

#ifndef GLOBALS_H
#define GLOBALS_H

extern bool eventTimer2;
extern bool eventTimer3;
extern bool eventTimer4;
extern bool eventTimer5;

extern unsigned adc1SampleBufferIndex;
extern unsigned short adc1SamplesBuffer[4];
extern bool adc1SampleBufferFull;

#endif /* GLOBALS_H */

• MAIN Code
  

int16_t main(void) {
    // Configurazione oscillatore a 40 MHz
    configureOscillator();

    // Abilitazione led
    enableLed(EXP16_LED_D3);
    enableLed(EXP16_LED_D4);
    enableLed(EXP16_LED_D5);

    // Abilitazione pulsanti
    ButtonData dataS3;
    enableButton(&dataS3, EXP16_BUTTON_S3);
    ButtonData dataS6;
    enableButton(&dataS6, EXP16_BUTTON_S6);
   
    // Inizializzazione Uart
    initUart2();
   
    // Inizializzazione ADC1
    initTimer5(1875,PRESCALER_1_64); // Inizializzazione del Timer 5 (che da il trigger all'ADC) a T=3ms
    initADC1(); // Inizializzazione ADC1

    switchLedOn(EXP16_LED_D3);
   
    // Attesa avvio da parte dell'utente
    while(!isButtonPressed(&dataS3));
   
    // Avvio periferiche
    startTimer5();
    startADC1();
    switchLedOn(EXP16_LED_D4);
   
    // Ciclo infinito
    while (true) {
        while(!adc1SampleBufferFull);
        // Channel 1
        writeWordOnUart2Channel(UART_CHANNNEL_1,adc1SamplesBuffer[0]);
        // Channel 2
        writeWordOnUart2Channel(UART_CHANNNEL_2,adc1SamplesBuffer[1]);
        // Channel 3
        writeWordOnUart2Channel(UART_CHANNNEL_3,adc1SamplesBuffer[2]);
        // Channel 4
        writeWordOnUart2Channel(UART_CHANNNEL_4,adc1SamplesBuffer[3]);
        
        adc1SampleBufferFull = false;
        
        toggleLed(EXP16_LED_D5);
    }
}

• ADC Code
  

.H

#ifndef ANALOGDIGITALCONVERTERS_H
#define ANALOGDIGITALCONVERTERS_H

#include
#include
#include
#include "globals.h"

#define ADC_TRIGGER_TIMER_T5_T3 0b100 //ADC1 attivato dal Timer5, ADC2 attivato dal Timer3
#define ADC_TRIGGER_TIMER_T3_T5 0b010 //ADC1 attivato dal Timer3, ADC2 attivato dal Timer5

void initADC1(void);

void startADC1(void);

void __attribute__((__interrupt__, __auto_psv__)) _ADC1Interrupt(void);

#endif /* ANALOGDIGITALCONVERTERS_H */



.C

#include "analogDigitalConverters.h"

void initADC1(void) {
    // Configurazioni generali
    AD1CON1bits.AD12B = 0; // Modalità 10 bit 16.4.1
    AD1CON2bits.CHPS1 = 1; // Quad channel 16.4.2
    AD1CON1bits.FORM = 0; // Formato unsigned integer 16.4.5
    AD1CON2bits.VCFG = 0; // Tensioni di riferimento interne 16.4.3
    AD1CON1bits.SIMSAM = 1; // Campionamento simultaneo 16.3.6
    AD1CON2bits.ALTS = 0; // Modalità non alternata 16.6.1
   
    // Configurazioni relative alle tempistiche
    AD1CON1bits.ASAM = 1; // Il campionamento inizia automaticamente 16.3.1
    AD1CON1bits.SSRC = ADC_TRIGGER_TIMER_T5_T3; // La conversione inizia col Timer 5 16.3.2
    // AD1CON3bits.SAMC // Non serve poichè SSRC!=7 16.3.1 (Nota 1 pag 16-11)
   
    // Configurazioni relative al clock
    AD1CON3bits.ADRC = 0; // Utilizza il clock di istruzioni FCY 16.4.4
    AD1CON3bits.ADCS = 2; // Settaggio divisore clock istruzioni 16.4.4
                                                // ADC Conversion Period ==> TAD = TCY * (ADCS + 1) = (1/40M) * 3
                                                // = 75 ns (13.3 MHz)
                                                // ADC Conversion Time for 10-bit ==> Tconv = 12 * TAD = 900 ns (1.1 MHz)
   
    // Configurazioni relative all'interrupt
    AD1CON2bits.SMPI = 1; // Genera un interrupt ogni conversione 16.5
                                                // (ogni 4 essendo in modalità 4 canali simultanei)
    IFS0bits.AD1IF = 0; // Pulisce l'interrupt flag per l'ADC1
    IEC0bits.AD1IE = 1; // Abilita l'interrupt per l'ADC1
   
    // Configurazioni relative ai canali
    AD1CHS0bits.CH0SA = 3; // CH0+ = AN3 16.6.1 (Table 16-10)
    AD1CHS0bits.CH0NA = 0; // CH0- = Vref- "
    AD1CHS123bits.CH123SA = 0; // CH123+ = AN0,AN1,AN2 "
    AD1CHS123bits.CH123NA = 0; // CH123- = Vref- "
}

void startADC1(void) {
    AD1CON1bits.ADON = 1; // Accensione 16.4.9
}

void __attribute__((__interrupt__,__auto_psv__)) _ADC1Interrupt(void) {
    adc1SamplesBuffer[adc1SampleBufferIndex] = ADC1BUF0;
    adc1SampleBufferIndex = (adc1SampleBufferIndex + 1) % 4;
    if (adc1SampleBufferIndex == 0) {
        adc1SampleBufferFull = true;
    }
    IFS0bits.AD1IF = 0; // Pulisce l'interrupt flag per l'ADC1
}

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