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From: bharath reddy sareddy on 12 Jan 2010 04:08
hi frds

im using dsPIC33FJ128GP802 for my application
im trying with ADC-DAC loop back as intial step.
my ADC is working finely
but i have a strange problem with DAC..........
intially data register(DAC1RDAT) is loading with default value and
then always it is going to zero..............
i have tried with the example given by microchip also.....it is also
giving the same problem
i m not geting where is the mistake
is there any thing wrong with device or code
here is the code i have taken


// Internal FRC Oscillator
_FOSCSEL(FNOSC_FRC); // FRC Oscillator
_FOSC(FCKSM_CSECMD & OSCIOFNC_ON & POSCMD_NONE);
// Clock Switching is enabled and
Fail Safe Clock Monitor is disabled
// OSC2 Pin Function: OSC2 is
Clock Output
// Primary Oscillator Mode:
Disabled

_FWDT(FWDTEN_OFF); // Watchdog Timer Enabled/
disabled by user software
// (LPRC can be disabled by
clearing SWDTEN bit in RCON register

int main (void)
{
// Configure Oscillator to operate the device at 40MIPS
// Fosc= Fin*M/(N1*N2), Fcy=Fosc/2
// Fosc= 7.37M*43/(2*2)=79.22Mhz for ~40MIPS input clock
PLLFBD=41; // M=43
CLKDIVbits.PLLPOST=0; // N1=2
CLKDIVbits.PLLPRE=0; // N2=2
OSCTUN=0; // Tune FRC oscillator, if FRC
is used

// Disable Watch Dog Timer
RCONbits.SWDTEN=0;

// Clock switch to incorporate PLL
__builtin_write_OSCCONH(0x01); // Initiate Clock Switch
to
// FRC with PLL (NOSC=0b001)
__builtin_write_OSCCONL(0x01); // Start clock switching
while (OSCCONbits.COSC != 0b001); // Wait for Clock switch
to occur

// Wait for PLL to lock
while(OSCCONbits.LOCK!=1) {};


initAdc(); // Initialize the A/D
converter to convert Channel 4
initDac(); // Initialize the D/A
converter
initDma0(); // Initialize the DMA
controller to buffer ADC data in conversion order
initTmr3(); // Initialize the Timer to
generate sampling event for ADC

extern fractional BufferA[NUMSAMP]; // Ping pong buffer A
extern fractional BufferB[NUMSAMP]; // Ping pong buffer B
extern unsigned int DmaBuffer; // DMA flag
extern int flag; // Flag
int i;

while (1) // Loop Endlessly -
Execution is interrupt driven
{
if(flag)
{
for(i = 0; i < NUMSAMP; i++)
{
while(DAC1STATbits.REMPTY != 1);// Wait for D/A conversion
if(DmaBuffer == 0)
DAC1RDAT = BufferA[i]; // Load the DAC buffer with
data
else
DAC1RDAT = BufferB[i]; // Load the DAC buffer with
data
}
flag = 0;
}
}

return 0;

}


#include "p33fxxxx.h"
#include "dsp.h"
#include "..\h\adcdacDrv.h"

fractional BufferA[NUMSAMP] __attribute__((space(dma))); // Ping-
pong buffer A
fractional BufferB[NUMSAMP] __attribute__((space(dma))); // Ping-
pong buffer B

/
*=============================================================================
initAdc() is used to configure A/D to convert channel 4 on Timer
event.
It generates event to DMA on every sample/convert sequence.
=============================================================================*/
void initAdc(void)
{
AD1CON1bits.FORM = 3; // Data Output Format: Signed
Fraction (Q15 format)
AD1CON1bits.SSRC = 2; // Sample Clock Source: GP Timer
starts conversion
AD1CON1bits.ASAM = 1; // ADC Sample Control: Sampling
begins immediately after conversion
AD1CON1bits.AD12B = 1; // 12-bit ADC operation

AD1CON2bits.CHPS = 0; // Converts CH0

AD1CON3bits.ADRC = 0; // ADC Clock is derived from Systems
Clock
AD1CON3bits.ADCS = 3; // ADC Conversion Clock Tad=Tcy*(ADCS
+1)= (1/40M)*4 = 100ns
// ADC Conversion Time for 12-bit Tc=14*Tad
= 1.4us

AD1CON1bits.ADDMABM = 1; // DMA buffers are built in
conversion order mode
AD1CON2bits.SMPI = 0; // SMPI must be 0


//AD1CHS0: A/D Input Select Register
AD1CHS0bits.CH0SA = 4; // MUXA +ve input selection (AN4)
for CH0
AD1CHS0bits.CH0NA = 0; // MUXA -ve input selection (Vref-)
for CH0

//AD1PCFGH/AD1PCFGL: Port Configuration Register
AD1PCFGL=0xFFFF;
AD1PCFGLbits.PCFG4 = 0; // AN4 as Analog Input


IFS0bits.AD1IF = 0; // Clear the A/D interrupt flag bit
IEC0bits.AD1IE = 0; // Do Not Enable A/D interrupt
AD1CON1bits.ADON = 1; // Turn on the A/D converter
}

/
*=============================================================================
initDac() is used to configure D/A.
=============================================================================*/
void initDac(void)
{
/* Initiate DAC Clock */
ACLKCONbits.SELACLK = 0; // FRC w/ Pll as Clock Source
ACLKCONbits.AOSCMD = 0; // Auxiliary Oscillator Disabled
ACLKCONbits.ASRCSEL = 0; // Auxiliary Oscillator is the Clock
Source
ACLKCONbits.APSTSCLR = 7; // FRC divide by 1

DAC1STATbits.ROEN = 1; // Right Channel DAC Output
Enabled

DAC1DFLT = 0x8000; // DAC Default value is the midpoint

// 103.16KHz // 8.038KHz //
44.211KHz // 25KHz
DAC1CONbits.DACFDIV = 5; //76; //
13; // 23; // // Divide High Speed Clock by DACFDIV+1

DAC1CONbits.FORM = 1; // Data Format is signed integer
DAC1CONbits.AMPON = 0; // Analog Output Amplifier is
enabled during Sleep Mode/Stop-in Idle mode

DAC1CONbits.DACEN = 1; // DAC1 Module Enabled
}

/
*=======================================================================================
Timer 3 is setup to time-out every Ts secs. As a result, the module
will stop sampling and trigger a conversion on every Timer3 time-out
Ts.
At that time, the conversion process starts and completes Tc=12*Tad
periods later.
When the conversion completes, the module starts sampling again.
However, since Timer3
is already on and counting, about (Ts-Tc)us later, Timer3 will expire
again and trigger
next conversion.
=======================================================================================*/
void initTmr3()
{
TMR3 = 0x0000; // Clear TMR3
PR3 = SAMPPRD; // Load period value in PR3
IFS0bits.T3IF = 0; // Clear Timer 3 Interrupt Flag
IEC0bits.T3IE = 0; // Clear Timer 3 interrupt enable bit

T3CONbits.TON = 1; // Enable Timer 3
}

/
*=============================================================================
DMA0 configuration
Direction: Read from peripheral address 0-x300 (ADC1BUF0) and write
to DMA RAM
AMODE: Register indirect with post increment
MODE: Continuous, Ping-Pong Mode
IRQ: ADC Interrupt
ADC stores results stored alternatively between BufferA[] and BufferB
[]
=============================================================================*/
void initDma0(void)
{
DMA0CONbits.AMODE = 0; // Configure DMA for Register
indirect with post increment
DMA0CONbits.MODE = 2; // Configure DMA for Continuous Ping-
Pong mode

DMA0PAD = (int)&ADC1BUF0; // Peripheral Address Register: ADC
buffer
DMA0CNT = (NUMSAMP-1); // DMA Transfer Count is
(NUMSAMP-1)

DMA0REQ = 13; // ADC interrupt selected for DMA
channel IRQ

DMA0STA = __builtin_dmaoffset(BufferA); // DMA RAM Start Address
A
DMA0STB = __builtin_dmaoffset(BufferB); // DMA RAM Start Address B

IFS0bits.DMA0IF = 0; // Clear the DMA interrupt flag bit
IEC0bits.DMA0IE = 1; // Set the DMA interrupt enable bit

DMA0CONbits.CHEN = 1; // Enable DMA channel
}

/
*=============================================================================
_DMA0Interrupt(): ISR name is chosen from the device linker script.
=============================================================================*/
unsigned int DmaBuffer = 0;
int flag = 0;

void __attribute__((interrupt, no_auto_psv)) _DMA0Interrupt(void)
{
DmaBuffer ^= 1; // Ping-pong buffer select flag
flag = 1; // Ping-pong buffer full flag
IFS0bits.DMA0IF = 0; // Clear the DMA0 Interrupt Flag
}

/
*=============================================================================
_DAC1RInterrupt(): ISR name is chosen from the device linker script.
=============================================================================*/
void __attribute__((interrupt, no_auto_psv)) _DAC1RInterrupt(void)
{
IFS4bits.DAC1RIF = 0; // Clear Right Channel Interrupt
Flag
}








if any body already worked on DAC of dsPIC33FJ128GP802

plz help me...................my project has stucked at this
point.............its very urgent for me

thnks to all in advance
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