PIC18 ADC measureing issue

[Prince Vegeta]

Hi

I need to continuously measure feedback voltage from a boost output. I wrote a code but I don't see that it does it correctly...

It should increase/decrease duty cycle in certain circumstances (assumed by me - I am still waiting for someone else to calculate the real ones)...

here's the code:

void main() {
     PORTE = 0;
     TRISE = 0;
     TRISA = 1;
     PORTA = 0;
     
     k_op = 204;
     k_min = 179;
     k_max = 230;

     v_op = 819;
     v_min = 717;
     v_max = 922;
     
     
     CCP4CON = 10;
     CCPR4H = 0x9C;
     CCPR4L = 0x40;

     CCP4IE_bit = 1;
     CCP4IF_bit = 0;
     GIE_bit = 1;
     PEIE_bit = 1;

     T3CON = 0x41; //Prescaler 1:1, start Timer 1


     ADCON1 = 0x0E;           // Configure AN0 pins as analog
     ADCON0 = 1;              // Configure ADC to work with channel 0 (AN0-RA0)
     delay_ms(1);             // Required for ADC to work properly
     ADCON2 = 0x06;
     CMCON  |= 7;             // Disable comparators
     GO_bit = 1;              // Start convertion
     
     CCP1CON = 0x0C;          // CCP1 configured as PWM (RC2 pin)
     k = 127;
     PWM1_init (1000);
     PWM1_set_duty (k);    // initialize PWM with 80% duty cycle
     PWM1_start();

  
  
     while(1){
     //Do whatever else is required

     v = ADC_Read (0);          // read boost's output voltage

     /////* duty cycle control */////
     
     if ( v >= 819 ) {         // if output voltage >= reference value:
     
        if ( v >= 922 ) {      // if output voltage exceeds max voltge, then:
        
          k = k_max;           // output max duty cycle then,
          k--;                 // decrease duty cycle
          }
     }
     
     if ( v <= 819 ) {         // if output voltage <= reference value:
     
        if ( v <= 717 ) {      // if output voltage is below min voltage, then:
        
          k = k_min;           // output min duty cycle then,
          k++;                 // increase duty cycle
          
          }
     }
     

     
     




     }    // end while loop
}         // end main loop

never mind any undefined variables cuz i defined them (I only pasted this part of code), also some parts here does other things, I only need to check the ADC stuff.

sim in proteus.

thanks

 

[Tahmid]

Ensure that the variable v is defined as a 16-bit variable.

For the duty cycle update part, instead of this:

     if ( v >= 819 ) {         // if output voltage >= reference value:
     
        if ( v >= 922 ) {      // if output voltage exceeds max voltge, then:
        
          k = k_max;           // output max duty cycle then,
          k--;                 // decrease duty cycle
          }
     }
     
     if ( v <= 819 ) {         // if output voltage <= reference value:
     
        if ( v <= 717 ) {      // if output voltage is below min voltage, then:
        
          k = k_min;           // output min duty cycle then,
          k++;                 // increase duty cycle
          
          }
     }

Use this:

     if ( v >= 819 ) {         // if output voltage >= reference value:
     
        if ( v >= 922 ) {      // if output voltage exceeds max voltge, then:
        
          k = k_max;           // output max duty cycle then,

          }

          k--;                 // decrease duty cycle

     }
     
     if ( v <= 819 ) {         // if output voltage <= reference value:
     
        if ( v <= 717 ) {      // if output voltage is below min voltage, then:
        
          k = k_min;           // output min duty cycle then,

          }

          k++;                 // increase duty cycle
     }

     PWM1_Set_Duty(k); //Assign k to duty cycle

Hope this helps.
Tahmid.

 

[Prince Vegeta]

you are right about this code! I don't know how I forgot to decrease/increase duty... I did it when max/min overridden but I should use it always.

so, will this be enough to measure and update duty?


about variable v as 16-bit, u mean define it as unsigned long?

____

I see some codes use #define stuff and I wonder what it does... also when the say something like c |=0 rather than c =0... do you know a thread/doc that explain these stuff?

thank you for your help.

 

[Tahmid]

you are right about this code! I don't know how I forgot to decrease/increase duty... I did it when max/min overridden but I should use it always.

so, will this be enough to measure and update duty?

You will probably need to slow it down more. Currently it's probably too fast.

about variable v as 16-bit, u mean define it as unsigned long?

No. Unsigned long is a 32-bit data type, for mikroC at least. Unsigned int is a 16-bit data type.

I see some codes use #define stuff and I wonder what it does... also when the say something like c |=0 rather than c =0... do you know a thread/doc that explain these stuff?

Read up on logical operators:
https://en.wikipedia.org/wiki/Operators_in_C_and_C++#Logical_operators
https://www.mikroe.com/download/eng/documents/compilers/mikroc/pro/pic/help/logical_operators.htm
https://www.mikroe.com/download/eng/documents/compilers/mikroc/pro/pic/help/bitwise_operators.htm

Check the mikroC PRO for PIC manual:

Hope this helps.
Tahmid.

 

[Prince Vegeta]

it's too fast? you mean in real life or for the sake of Proteus simulation?

for simulation, I slowed the PWM freq to 1Khz to be able to notice the difference, it did help but not that much.

I choose 25Khz cuz it's too fast and it will update fast which is very useful in real life. So I went with "faster is better"... Is it wrong?