MCP4921 with PIC16F877A

[MrElectroniceng]

Dear all,

I am trying to communicate PIC16F877A with MCP4921, which is a serial input DAC. I am using HI TECH C compiler for the code. I could not achieve to obtain analog output. I tried many things, still couldn't work. The design and the code is below. How can I fix it? Where is my mistake?

Thank you in advance.

#include <htc.h>
#include <stdio.h>
#include <stdlib.h>
#define _XTAL_FREQ 20000000

#define DAC_CS     RB7
#define DAC_SCK    RB6
#define DAC_SDI    RC0
#define DAC_LDAC   RC1


void init_dac()
{
   DAC_CS = 0b1;
   DAC_LDAC = 0b1;
   DAC_SCK = 0b1;
   DAC_SDI = 0b1;
}

void write_dac(unsigned int data) {
   unsigned char i;
   unsigned short long tobesent;
   
   tobesent = (short)0x030000UL || data;                 
   
   DAC_LDAC = 0b1;
   DAC_SCK = 0b0;
   DAC_CS = 0b0;

   for(i=0; i<=23; ++i)
   {
		__delay_us(10);

      if(i<4 || (i>7 && i<12))
         tobesent = tobesent << 1u;
      else
      {
		 DAC_SDI = (bit) (tobesent / (short) 0x800000UL);
		 //DAC_SDI = 0b1;
		 tobesent = tobesent << 1u;
         DAC_SCK = 0b1;
         DAC_SCK = 0b0;
      }
   }
   DAC_CS = 0b1;

   DAC_LDAC = 0b0;
   __delay_us(10);
   
   DAC_LDAC = 0b1;
}

#include <htc.h>
#include <stdio.h>
#include <stdlib.h>

#define _XTAL_FREQ 20000000  

#include "mcp4921.h"


__CONFIG(HS & WDTDIS & PWRTEN & BOREN & LVPEN & WRTEN &
DEBUGDIS & DUNPROT & UNPROTECT);




void init(void) {


	TRISA = 0b111110;		
	TRISB = 0b00000000;  
	TRISC = 0b00000000;		
	TRISD = 0b00000000;		
	TRISE = 0b100;			
	
	PORTA = 0x00;
	PORTB = 0x00;
	PORTC = 0x00;
	PORTD = 0x00;
	PORTE = 0x00;

	OPTION = 0b10000000;  	
						  	
	
	INTCON = 0b01100000;	
							

	T1CON=0b00110101;		
							
						

	ADCON1=0x0f;			

}





void main(void) {
	init();
	init_dac();

	while(1) {
		write_dac(0x0000);
		__delay_ms(1000);
		write_dac(0x77F0);
		__delay_ms(1000);
		write_dac(0x77FF);
		__delay_ms(1000);
	}
}

View attachment TEST_DAC.zip

 

[milan.rajik]

No time to test the code by creating a project in MPLAB and Proteus. If possible zip and attach complete MPLAB Hi-Tech PICC project files + Proteus file.

 

[MrElectroniceng]

I attached the file with error. It is under the code part in the first post.

Thank you

 

[MrElectroniceng]

I figured that out myself. It works now.

Thank you

 

[milan.rajik]

Working code attached.

 

[MrElectroniceng]

Thank you very much, milan.rajik. The code works great!! When fixing the code I used SPI property of the pic but your code looks more efficient. If you want I can upload my code.

 

[milan.rajik]

Upload your code. Yours is hardware SPI code and mine is software SPI code. For software SPI you can use any digital IO pin(s) for interfacing SPI device to MCU.

 

[MrElectroniceng]

The SPI code is attached.

View attachment TEST_DAC.zip