PIC16f877 / LM35 temperature sensor / max232 / C-code issue

//program for temperature monitoring system written for PIC16F877A //

//author: keshava murali //

//version1 //

//bellow 30ºC LED switches OFF //above 40ºC LED switches ON //

//between 30ºC and 40ºC LED toggles //

//timer delay~0.5sec //

//9/11/07 //

// Compiler: MikroC for PIC - V. 5.0.0.3 //

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

#define LED PORTB.F1 //LED port pin

#define max_count 15

#define low_temp 25 //define lower temperature range

#define high_temp 31 //define higher temperature range

//Function declarations

void send_data(unsigned char *p,unsigned char no_of_bytes);

unsigned char hex_to_ascii(unsigned char number);

//global variable declarations

unsigned short int timer_counter=0;

unsigned char mes_temp[]={"temp:"},mes_sensor[]={"sdata: "};

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

//timer 0 ISR; increments timer_counter ; reinitializes TMR0 //

//input: none output: none affected: timer_counter, TMR0,INTCON //

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

void interrupt() //timer0 interrupt

{

  timer_counter++; //increment counter

  TMR0 = 96; //reinitialize TMR0 register

  INTCON.TMR0IF=0; //clear timer0 overflow interrupt flag bit

}

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

////main program starts here; reads ADC channel 0; calibrates the sensor data; //

////sends to serial port //

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

void main(void)

{

  unsigned char sensor_data,sensor_data1,sensor_data2,high_temp_flag,low_temp_flag,med_temp_flag,i;

  TRISA=0xFF; //configure PORTA as input

  TRISB=0; //configure PORTB as output

  PORTA=0; //clear PORTA

  PORTB=0; //clear PORTB

  Usart_Init(9600); //initialize serial port using built in function

//if built in function is not used then use bellow commented //codes to initialize serial port

//SPBRG=103; //for 9600 baud rate (with 4MHz)

//TXSTA=0x22; //8 bit transmission, asynchronous, low baud rate, no parity

//RCSTA=0x90; //8 bit receive, enable serial port, no parity

//PIE1.RCIE=1; //enable receive interrupt

//PIE1.TXIE=1; //enable transmission interrupt

//Configure A/D

  ADCON0=0x80; //Fosc/32, AN0, A/D disabled

  ADCON1=0x80; //right justified, Fosc/32, analog inputs

  ADCON0.ADON=1; //enable ADC module

  OPTION_REG=0b00000111; //disable portb pullup, -ve edge, internal clock, increment

//on +ve edge, prescalar-0:256

  INTCON.TMR0IE=1; //enable timer0 interrupt

  INTCON.PEIE=1; //enable peripheral interrupts

  INTCON.GIE=1; //enable global interrupt

  for (;;) //infinite loop

    {

      INTCON.TMR0IE=1; //enable timer 0 interrupt

      while (timer_counter!=max_count) //timer0 delay; wait till delay elapsed

        {
          asm nop;
        }

      timer_counter=0; //delay over; reinitialize counter

//Delay_ms(450); //without timer delay we can use built in delay function

      sensor_data=Adc_Read(0); // read A/D using built in function

// if you don’t want to use built in function then use //bellow commented code

//ADCON0.GO=1; //start A/D conversion

//while(ADCON0.GO){} //wait till A/D conversion is over (1.6µS )

//sensor_data=ADRESL; //get ADC data; lower byte is sufficient

      for (i=0; i<=5; i++) //send message to serial port

        {
          Usart_Write(mes_sensor[i]);
        }

//send_data(&mes_sensor,sizeof(mes_temp)); //no built in function-use this function

      sensor_data1=sensor_data/2; //calibrate sensor data

      sensor_data2=sensor_data1; //temporarily store calibrated temperature

      sensor_data1=hex_to_ascii((sensor_data/10)); //do hex to ascii conversion of MSB digit

      Usart_Write(sensor_data1); //send to serial port

//don’t want built in function-use bellow two codes

//while(!TXIF){} //if transmit buffer is empty put data else wait

//TXREG=sensor_data1; //send to serial port

      sensor_data1=hex_to_ascii((sensor_data%10));//hex to ascii conversion of LSB digit

      Usart_Write(sensor_data1); // send to serial port

//while(!TXIF){} //if transmit buffer is empty put data else wait

//TXREG=sensor_data1; //send to serial port

      if (sensor_data2>high_temp) //check for temperature range

        {
          high_temp_flag=0xFF; //if temperature > 40ºC set high_temp_flag

          low_temp_flag=0x00;
        } //clear low_temp_flag

      else if (sensor_data2<high_temp && sensor_data2>low_temp)

        {
          low_temp_flag=0x00; //if temperature <>

          high_temp_flag=0x00;
        } //clear high_temp_flag

      else

        {
          low_temp_flag=0xFF;

          high_temp_flag=0x00;
        } //to avoid false triggering of LED clear both temp flags

      if (high_temp_flag==0xFF) //check flag conditions;

        LED=1; //if high_temp_flag is set switch ON LED

//PORTB.F1=1;

      else if (low_temp_flag==0xFF) //if low_temp_flag is set switch OFF LED

        LED=0;

//PORTB.F1=0;

      else //if temperature is in between 30ºC and 40ºC blink LED

        LED=~LED; //toggle LED

//PORTB.F1= ~PORTB.F1;

      for (i=0; i<=4; i++) //send temperature to serial port

        {
          Usart_Write(mes_temp[i]);    //send message to serial port
        }

//send_data(&mes_temp,sizeof(mes_temp)); //don’t want built in?-use this function

      sensor_data1=hex_to_ascii((sensor_data2/10)); //hex to ASCII convesion of MSB digit

      Usart_Write(sensor_data1); //send to serial port;

//while(!TXIF){} //if transmit buffer is empty put data else wait

//TXREG=sensor_data1; //send to serial port

      sensor_data1=hex_to_ascii((sensor_data2%10));//hex to ASCII convesion of LSB digit

      Usart_Write(sensor_data1); //send to serial port

//while(!TXIF){} //if transmit buffer is empty put data else wait

//TXREG=sensor_data1; //send to serial port

    }

}

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

//function to convert hex number to ASCII format //

//input: unsigned char hex number return: unsigned char ASCII equivalent //

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

unsigned char hex_to_ascii(unsigned char number)

{

  if (number<10) //if hex number is 0 to 9 add 0x30

    number=number+0x30;

  else //if hex number is A to F add 0x37

    number=number+0x37;

  return(number); //return ASCII equivalent

}

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

//function to send a character to serial port //

//use this function if USART built in function is not used //

//input: starting address of the string, length of the string return: none //

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////



void send_data(unsigned char *p,unsigned char no_of_bytes)

{
  unsigned char i;

  for (i=0; i<=7; i++)

    {

      while (!TXIF) {} //if transmission buffer is full wait

      TXREG=*(p+i); //send character to serial port

    }

}

unsigned char hex_to_ascii(unsigned char number)

{ //if hex number is 0 to 9 add 0x30

if(number<10)

number=number+0x00;

else //if hex number is A to F add 0x37

number=number+0x00;

return(number); //return ASCII equivalent

}