DAC

molto bene mauro funziona cambiando il Pin. E' normale non ottenere un onda sinusoidale ma un onda quadra smussata?

Ciao purtroppo sono de coccio, mi serve aiuto ho cercato di usare i tuoi consigli ma celo fatta in parte, ora se premo RB0 esce la frequenza fissata, la nota negativa è che se rilascio il pulsante vi è una frequenza indesiderata sotto fondo, mi dai ancora una mano?
SE puo servire uso un quaezo da 4 MHz.
Ecco il codice, lo ripulito dei DEFINE e il modulo USB, vi ho aggiunto il pulsante.


#include <p18f4550.h>
#include <portb.h>

#pragma config FOSC = HS
#pragma config WDT = OFF
#pragma config LVP = OFF
#pragma config PBADEN = OFF

//OSC = HS Set to work for high speed
//WDT = OFF watchdog timer is off
//LVP = OFF LVP programming is off
//PBADEN = OFF Analog input on PORTB are off

//************************************************************
// Functions Prototypes
//************************************************************
void set_duty_cycle (int duty_cycle);
void turn_on_PWM1 (void);
void High_Int_Event (void);


//************************************************************
// Global variables
//************************************************************

//Samples
int sine[] = {250,299,346,389,427,458,481,495,500,495,481,458,427,389,346,299,250,201,154,111,73,42,19,5,0,5,19,42,73,111,154,201};

// Repeat the sample for x time
// sampling frequency must be changed to keep analog signal frequency costnat
const unsigned char REPEATING_FACTOR = 3;


//************************************************************
// Interrupt Handler
//************************************************************

#pragma code high_vector = 0x08
void high_interrupt (void) {
// go to the interrupt handler
_asm GOTO High_Int_Event _endasm
}

#pragma code
#pragma interrupt High_Int_Event

void High_Int_Event (void) {

static unsigned char sample = 0;
static unsigned char repeat = 0;

if (PIR1bits.TMR2IF == 1) {
if (PORTBbits.RB0 == 0) {

// I create a pulse on RC0 to be measured with the scope.
// Used just for debugging the sampling frequency
LATCbits.LATC2 = 1;
LATCbits.LATC2 = 0;
if (PORTBbits.RB0 == 0) {

set_duty_cycle (sine[sample]);
}
else {
set_duty_cycle (0);
}
repeat++;
}



if (repeat == REPEATING_FACTOR) {
repeat = 0;
sample++;

if (sample > 31) {
sample = 0;
}
}

}


//Clear Timer 2 Interrupt Flag
PIR1bits.TMR2IF = 0;
}


//************************************************************
// Main program
//************************************************************

void main (void){

// PORTA settings
LATA = 0x00;
TRISA = 0xFF;

// PORTB settings
LATB = 0x00;
TRISB = 0xFF;

// PORTC settings
LATC = 0x00;
TRISC = 0b11111010;

// PORTD settings
LATD = 0x00;
TRISD = 0x00;

// PORTE settings
LATE = 0x00;
TRISE = 0xFF;



//*************************************
// Modules Initializaion
//*************************************

// Set the PWM frequency to
PR2 = 198;

set_duty_cycle (250);

// Turn ON TMR2 and set Prescaler to 0
T2CON = 0x04;

turn_on_PWM1 ();

// Enable Timer 2 Interrupt
PIE1bits.TMR2IE = 1;

// Standrd interrupt (by default is already 0)
RCONbits.IPEN = 0;

// Enable global interrupt
INTCONbits.GIE = 1;

// Enable Peripheral Interrupt
INTCONbits.PEIE = 1 ;

// just loop for nothing...
while (1){

}
}


//************************************
// Set the Diuty Cicle
//************************************

void set_duty_cycle (int duty_cycle) {

CCPR1L = (unsigned char) (duty_cycle >> 2);

if (duty_cycle & 0x0001)
CCP1CONbits.DC1B0 = 0x0001;
else
CCP1CONbits.DC1B0 = 0x0000;

if (duty_cycle & 0x0002)
CCP1CONbits.DC1B1 = 0x0001;
else
CCP1CONbits.DC1B1 = 0x0000;
}


//************************************
// Turn ON the PWM module
//************************************
void turn_on_PWM1 (void) {

CCP1CON = CCP1CON | 0b00001100;

}

Ciao, ho letto l'articolo che mi hai passato come link, ma preferisco il tuo sistema se riesco a risolvere i problemi perchè il DAC del link mi richiede troppi pin.
Ho cercato di tradurlo se a qualcuno interessa le passo la traduzione.
Grazie

bene,
...ora funziona.
Qualche altro accorgimento e ci siamo.

relativamente al pin RC0 non vedi nulla perche' il pin viene cambiato da 1 a 0 troppo rapidamente (un solo ciclo istruzioni).
Per visualizzare questo impulso ho fatto uso di un oscilloscopio con campionamento a 1GS/s e banda da 40MHz mentre nel tuo caso campioni a 44KHz e banda 20KHz. Quindi l'impulso e' troppo rapido per essere letto.

Per togliere il rumore prova a spegnere il modulo PWM piuttosto che porre il Duty Cycle a 0.
In alternativa metti il Duty cycle a 1023 (ovvero sempre a 1).

Saluti,

Mauro

Ciao, ho provato ma non va, ho scritto prima e seconda prova nel codice per vedere se ho fatto bene.
codice:

#include <p18f4550.h>
#include <portb.h>

#pragma config FOSC = HS
#pragma config WDT = OFF
#pragma config LVP = OFF
#pragma config PBADEN = OFF

//OSC = HS Set to work for high speed
//WDT = OFF watchdog timer is off
//LVP = OFF LVP programming is off
//PBADEN = OFF Analog input on PORTB are off

//************************************************************
// Functions Prototypes
//************************************************************
void set_duty_cycle (int duty_cycle);
void turn_on_PWM1 (void);
void High_Int_Event (void);


//************************************************************
// Global variables
//************************************************************

//Samples
int sine[] = {250,299,346,389,427,458,481,495,500,495,481,458,427,389,346,299,250,201,154,111,73,42,19,5,0,5,19,42,73,111,154,201};

// Repeat the sample for x time
// sampling frequency must be changed to keep analog signal frequency costnat
const unsigned char REPEATING_FACTOR = 3;


//************************************************************
// Interrupt Handler
//************************************************************

#pragma code high_vector = 0x08
void high_interrupt (void) {
// go to the interrupt handler
_asm GOTO High_Int_Event _endasm
}

#pragma code
#pragma interrupt High_Int_Event

void High_Int_Event (void) {


static unsigned char sample = 0;
static unsigned char repeat = 0;




if (PIR1bits.TMR2IF == 1) {



if (PORTBbits.RB0 == 0) {

set_duty_cycle (sine[sample]);

repeat++;
}

else {
//ClosePWM1 (); prima prova fatta (non funziona, non esce la frequenza)

//set_duty_cycle (1023); seconda prova fatta (il rumore rimane, cambia la Freq.)


set_duty_cycle (0);
}

if (repeat == REPEATING_FACTOR) {
repeat = 0;
sample++;
}
if (sample > 31) {
sample = 0;
}
}

//Clear Timer 2 Interrupt Flag
PIR1bits.TMR2IF = 0;

}


//************************************************************
// Main program
//************************************************************

void main (void){

// PORTA settings
LATA = 0x00;
TRISA = 0xFF;

// PORTB settings
LATB = 0x00;
TRISB = 0xFF;

// PORTC settings
LATC = 0x00;
TRISC = 0b11111010;

// PORTD settings
LATD = 0x00;
TRISD = 0x00;

// PORTE settings
LATE = 0x00;
TRISE = 0xFF;



//*************************************
// Modules Initializaion
//*************************************

// Set the PWM frequency to
PR2 = 198;

set_duty_cycle (250);

// Turn ON TMR2 and set Prescaler to 0
T2CON = 0x04;

turn_on_PWM1 ();

// Enable Timer 2 Interrupt
PIE1bits.TMR2IE = 1;

// Standrd interrupt (by default is already 0)
RCONbits.IPEN = 0;

// Enable global interrupt
INTCONbits.GIE = 1;

// Enable Peripheral Interrupt
INTCONbits.PEIE = 1 ;

// just loop for nothing...
while (1){
}
}


//************************************
// Set the Diuty Cicle
//************************************

void set_duty_cycle (int duty_cycle) {

CCPR1L = (unsigned char) (duty_cycle >> 2);

if (duty_cycle & 0x0001)
CCP1CONbits.DC1B0 = 0x0001;
else
CCP1CONbits.DC1B0 = 0x0000;

if (duty_cycle & 0x0002)
CCP1CONbits.DC1B1 = 0x0001;
else
CCP1CONbits.DC1B1 = 0x0000;
}


//************************************
// Turn ON the PWM module
//************************************
void turn_on_PWM1 (void) {


CCP1CON = CCP1CON | 0b00001100;

}