DAC0832 simulating with Proteus and Arduino

[pabspagg]

Hi,
I am doing a project for an electronic class I am taking.
What I have to do is : Using an arduino as a counter ( 8 bits Counter) connected to a DAC0832 and in the output generating a Sine wave ( I can't use arduino for generating the sine wave. I will use amp ops later ). The last part I haven't simulate yet.


The problem is the following: I want the wave output to be triangular at first, with steps ups and downs . But now I am only getting the steps going down ( I am using an AMP OP inverter) and it's not going up ( Why not? ) . As you can see in the image, the arduino code is working 100%. It's going from 0 to 255 then 255-0. ( I am only showing part of it).



Thanks a lot!
Sorry for the bad english

 

[ericgibbs]

hi p,
Look at this clip from the datasheet, the Vout polarity is negative.
E

 

[ericgibbs]

hi p,
Try to simulate this version of the circuit taken from the datasheet.
E

 

[pabspagg]

hi p,
Try to simulate this version of the circuit taken from the datasheet.
E
View attachment 104679

Thanks for the answer.

I just did . See what I got :


I am not sure if I was clear about what I want. The wave in the end should be like this ( With small steps increasing and decreasing ) . Do you know how can I fix ?:

 

[ericgibbs]

hi p,
If you post your program listing I am sure one of us could help.
Looking at your print out, you seem to be incrementing the DAC input, in one bit steps, the input inc/dec should follow a Sine wave sequence.
E

 

[Ian Rogers]

Can you post the code.... The simulation shows a ramp output... Its the code you need to change.. you have decreasing amounts going to the DAC but then when it hits bottom you need to slowly increase not start all over!!

 

[pabspagg]

Sure , here's the code :

void setup() {
 
   DDRD = 255;
}

void loop() {
 
  PORTD++;
  delay(100);
  if ( PORTD == 255){
    while ( PORTD != 0 ){
      PORTD--;
      delay(100);
      }
  }
}

// I'm using Port manipulation in arduino. https://www.arduino.cc/en/Reference/PortManipulation
Maybe that's the problem?

 

[Ian Rogers]

When portd-- != 0.... It'll mess up with this...

The easier way is an index

int inc = 1;
void setup() {
   PORTD = 0;
   DDRD = 255;
}

void loop()
   {
    PORTD += inc;
    delay(100);
     if ( PORTD > 254 ) inc = -1;
     if ( PORTD < 1 ) inc = 1;
    }

 

[pabspagg]

After trying a lot to solve the problem. The issue was indeed the code. It turned out that it wasn't a viable option using PORT manipulation on arduino .
Here's the new one .

int led[8] = {0,1,2,3,4,5,6,7};
boolean A[8];
int inc=1;
int saida=0;

void setup() {  
  for(int i=0;i<8;i++)  {   
    pinMode(led[i], OUTPUT);  
  }  
}

void loop() {  
  saida += inc;  
  if( saida > 254 )  {   
      inc= -1;  
    }  
  if( saida < 1 )  {   
      inc= 1;  
    }  
  conversor();  
 
  for(int i=0;i<8;i++)  {   
    digitalWrite(led[i],A[i]);  
  }  
}
void conversor(){
  int valor=saida;
  for(int i=0;i<8;i++)  {
      if(valor%2>0)    {
          A[i]=1;
        }
        else    {
          A[i]=0;
        }
      valor=(valor/2);
    }
  }

The output I am getting now. There's some noise. I'm still trying to figure out how to remove this.

 

[Ian Rogers]

The noise isn't software... This is because you dac is seeing the transition for level to level... The ouput buffer should be clocked only when the new data has been shifted in...