PIC18F4520 – Interfacing Temperature sensor

PIC18F4520 mini development board has on board temperature sensor MCP9700. Here in this section, we discuss the interfacing of the same with its host controller PIC18F4520. PIC18F4520 has 8 channel 10-bit successive approximation ADC.
On the Mini Development Board the temperature sensor MCP9700 is connected to pin RA1 of the controller i.e, channel1 via jumper J17. The MCP9700/9700A and MCP9701/9701A family of Linear Active Thermistor™ Integrated Circuit (IC) is an analog temperature sensor that converts temperature to analog voltage. It has an accuracy of ±2°C from 0°C to +70°C (MCP9700A/9701A) ±4°C from 0°C to +70°C (MCP9700/9701) while consuming 6µA (typical) of operating current. Sensitivity is 10mV/°C. At 0°C, the output is 500mV. So that’s the spec and description for MCP9700, now lets see its actual working here below.

Schematic

Note: To use temperature sensor, don’t forget to short jumper J17. Leaving it open frees RA1 and it can be used for any other desired purpose.

Sample Code

Sample code to check the temperature sensor is given below. The output is displayed on LCD.

/*************************************************************************
                           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,"Temp: ");	
 ADCON0 = 0x07;             
 ADCON1 = 0x0d;             
 ADCON2 = 0x80;  
 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      */
                                /* Converting to equivalent temp.        */
  ADC_Value = (((ADC_Value/204.5)-0.5)/0.01); 

  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(0X8A);
  for(k=2; k>=0; k--)
  {
   Data(ADC_Array[k]);          /* Display the result on LCD             */
  }
  Data(0xdf);
  Data('C');
 }
}        

/*************************************************************************
* 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  : Adr - 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,"Temp: ");

ADCON0 = 0x07;

ADCON1 = 0x0d;

ADCON2 = 0x80;

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 */

/* Converting to equivalent temp. */

ADC_Value = (((ADC_Value/204.5)-0.5)/0.01);

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(0X8A);

for(k=2; k>=0; k--)

{

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

}

Data(0xdf);

Data('C');

}

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

* 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 : Adr - 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

PIC18F4520 Mini Development Board – Overview
PIC18F4520 Mini Development Board – Interfacing LED
PIC18F4520 Mini Development Board – Interfacing LCD
PIC18F4520 Mini Development Board – Serial communication(USART)
PIC18F4520 Mini Development Board – Interfacing Switch
PIC18F4520 Mini Development Board – Interfacing Buzzer
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PIC18F4520 Mini Development Board – Interfacing Temperature sensor
PIC18F4520 Mini Development Board – Interfacing Servo Motor
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Resources

Softwares

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

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PIC18F4520 Mini Development Board – Overview says:

August 4, 2015 at 4:56 am

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