PIC18F4520 – Interfacing POT(ADC)

PIC18F4520 mini development board has a POT connected to pin RA0 i.e, channel0 via jumper J16. Sample code to check the ADC module of PIC18F4520 with potentiometer is given below. The output is displayed on LCD and the variation can be checked with the POT.

SchematicNote: To use potentiometer, don’t forget to short jumper J16. Leaving it open frees RA0 and it can be used for any other desired purpose.

Sample Code

/*************************************************************************
                           HEADER FILES
**************************************************************************/
#include<pic18.h>                   

/*************************************************************************
                       FUNCTION DECLARATIONS
**************************************************************************/
void Delay_us(int us);
void Data(int Value);           
void Cmd(int Value);            
void Send2LCD(const char Adr, const char *Lcd);

/*************************************************************************
                       VARIABLE DECLARATIONS
**************************************************************************/ 
int k,ADC_Value;
char ADC_Array[5];

/*************************************************************************
                           MAIN FUNCTION
**************************************************************************/
void main()                     
{
 TRISA = 0XFF;                  /* Set PORTA as input for channel 0      */
 TRISC = 0X00;                  /* PORTC(control lines) configured as o/p*/
 TRISD = 0X00;                  /* PORTD(data lines) configured as o/p   */
 Delay_us(25);            
 Cmd(0X30);
 Delay_us(25);                  /* LCD Specification Command             */
 Cmd(0X30);
 Delay_us(25);                  /* LCD Specification Command             */
 Cmd(0X30);
 Delay_us(25);                  /* LCD Specification Command             */
 Cmd(0X38);                     /* Double Line Display Command           */
 Cmd(0X06);                     /* Auto Increment Location Address       */
 Cmd(0X0C);                     /* Display ON Command                    */
 Cmd(0X01);                     /* Clear Display Command                 */
 Delay_us(1000);
 Send2LCD(0x80,"ADC Result: ");	
 ADCON0 = 0x01;                 /* ADON=1 and other bits configured as 0 */       
 ADCON1 = 0x00;                 /* All bits are configured as 0 in ADCON1*/               
 ADFM   = 1;                    /* Result format right justified         */
 ACQT1  = 1;                    /* A/D acqusition time select is 4TAD    */ 
 ADCS1  = 1;                    /* A/D conversion clock is Focs/32       */

 while(1)
 {
  GO = 1;                       /* Set A/D conversion status bit
                                   (conversion in progress)              */
  while(GO==1);                 /* Wait until A\D conversion completes   */
  ADC_Value = ADRESH;           /* Copy the 2 bits in ADRESH to ADC_Value*/
  ADC_Value = ADC_Value<<8;     /* Shift it 8 bits to left               */
  ADC_Value = ADC_Value+ADRESL; /* Add left shifted value to ADRESL      */

  for(k=0; k<=3; k++)           /* Convert the result into ASCII         */
  {                             /* Separate each digit of the integer    */
   ADC_Array[k] = ADC_Value%10+'0';
   ADC_Value    = ADC_Value/10;
  }
  Cmd(0X8C);
  for(k=3; k>=0; k--)
  {
   Data(ADC_Array[k]);          /* Display the result on LCD             */
  }
 }        
}

/*************************************************************************
* Function    : Cmd                                                      *
*                                                                        *
* Description : Function to send a command to LCD                        *
*                                                                        *
* Parameters  : Value - command to be sent                               *
**************************************************************************/
void Cmd(int Value)
{
 PORTD = Value;                 /* Write the command to data lines       */
 RC0   = 0;                     /* RS-0(command register)                */
 RC1   = 1;                     /* E-1(enable)                           */
 Delay_us(25);                
 RC1   = 0;                     /* E-0(enable)                           */
}

/*************************************************************************
* Function    : Data                                                     *
*                                                                        *
* Description : Function to display single character on LCD              *
*                                                                        *
* Parameters  : Value - character to be displayed                        *
**************************************************************************/
void Data(int Value)
{
 PORTD = Value;                 /* Write the character to data lines     */
 RC0   = 1;                     /* RS-1(data register)                   */
 RC1   = 1;                     /* E-1(enable)                           */
 Delay_us(25);                
 RC1   = 0;                     /* E-0(enable)                           */ 
}

/*************************************************************************
* Function    : Send2LCD                                                 *
*                                                                        *
* Description : Function to display string on LCD                        *
*                                                                        *
* Parameters  : loc - location                                           *
*               String to be displayed                                   *
**************************************************************************/
void Send2LCD(const char Adr, const char *Lcd)
{
 Cmd(Adr);                      /* Address of location to display string */
 while(*Lcd!='\0')              /* Check for termination character       */
 {
  Data(*Lcd);                   /* Display the character on LCD          */
  Lcd++;                        /* Increment the pointer                 */
 }     
}

/*************************************************************************
* Function    : Delay_us                                                 *
*                                                                        *
* Description : Function for 1 microsecond delay                         *
*                                                                        *
* Parameter   : us - delay in microseconds                               *
**************************************************************************/
void Delay_us(int us)
{
 us = us>>1;
 while(us!=1)
 us--;
}

/***************************  END OF PROGRAM  ****************************/

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/*************************************************************************

HEADER FILES

**************************************************************************/

#include<pic18.h>

/*************************************************************************

FUNCTION DECLARATIONS

**************************************************************************/

void Delay_us(int us);

void Data(int Value);

void Cmd(int Value);

void Send2LCD(const char Adr, const char *Lcd);

/*************************************************************************

VARIABLE DECLARATIONS

**************************************************************************/

int k,ADC_Value;

char ADC_Array[5];

/*************************************************************************

MAIN FUNCTION

**************************************************************************/

void main()

{

TRISA = 0XFF; /* Set PORTA as input for channel 0 */

TRISC = 0X00; /* PORTC(control lines) configured as o/p*/

TRISD = 0X00; /* PORTD(data lines) configured as o/p */

Delay_us(25);

Cmd(0X30);

Delay_us(25); /* LCD Specification Command */

Cmd(0X30);

Delay_us(25); /* LCD Specification Command */

Cmd(0X30);

Delay_us(25); /* LCD Specification Command */

Cmd(0X38); /* Double Line Display Command */

Cmd(0X06); /* Auto Increment Location Address */

Cmd(0X0C); /* Display ON Command */

Cmd(0X01); /* Clear Display Command */

Delay_us(1000);

Send2LCD(0x80,"ADC Result: ");

ADCON0 = 0x01; /* ADON=1 and other bits configured as 0 */

ADCON1 = 0x00; /* All bits are configured as 0 in ADCON1*/

ADFM = 1; /* Result format right justified */

ACQT1 = 1; /* A/D acqusition time select is 4TAD */

ADCS1 = 1; /* A/D conversion clock is Focs/32 */

while(1)

{

GO = 1; /* Set A/D conversion status bit

(conversion in progress) */

while(GO==1); /* Wait until A\D conversion completes */

ADC_Value = ADRESH; /* Copy the 2 bits in ADRESH to ADC_Value*/

ADC_Value = ADC_Value<<8; /* Shift it 8 bits to left */

ADC_Value = ADC_Value+ADRESL; /* Add left shifted value to ADRESL */

for(k=0; k<=3; k++) /* Convert the result into ASCII */

{ /* Separate each digit of the integer */

ADC_Array[k] = ADC_Value%10+'0';

ADC_Value = ADC_Value/10;

}

Cmd(0X8C);

for(k=3; k>=0; k--)

{

Data(ADC_Array[k]); /* Display the result on LCD */

}

/*************************************************************************

* Function : Cmd *

* *

* Description : Function to send a command to LCD *

* *

* Parameters : Value - command to be sent *

**************************************************************************/

void Cmd(int Value)

{

PORTD = Value; /* Write the command to data lines */

RC0 = 0; /* RS-0(command register) */

RC1 = 1; /* E-1(enable) */

Delay_us(25);

RC1 = 0; /* E-0(enable) */

}

/*************************************************************************

* Function : Data *

* *

* Description : Function to display single character on LCD *

* *

* Parameters : Value - character to be displayed *

**************************************************************************/

void Data(int Value)

{

PORTD = Value; /* Write the character to data lines */

RC0 = 1; /* RS-1(data register) */

RC1 = 1; /* E-1(enable) */

Delay_us(25);

RC1 = 0; /* E-0(enable) */

}

/*************************************************************************

* Function : Send2LCD *

* *

* Description : Function to display string on LCD *

* *

* Parameters : loc - location *

* String to be displayed *

**************************************************************************/

void Send2LCD(const char Adr, const char *Lcd)

{

Cmd(Adr); /* Address of location to display string */

while(*Lcd!='\0') /* Check for termination character */

{

Data(*Lcd); /* Display the character on LCD */

Lcd++; /* Increment the pointer */

}

/*************************************************************************

* Function : Delay_us *

* *

* Description : Function for 1 microsecond delay *

* *

* Parameter : us - delay in microseconds *

**************************************************************************/

void Delay_us(int us)

{

us = us>>1;

while(us!=1)

us--;

}

/*************************** END OF PROGRAM ****************************/

Topics related to PIC18F4520 Mini Development Board

Resources

Softwares

Datasheets
- PIC18F4520
- MCP9700
- MAX232
- CP2102
- LM7805
- LD1117
- LCD (16×2)

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