[PIC] Problem with frequency counter based on PIC16f877a

[RAJPUT VIDISHA]

hi...
guys really need help in making frequency counter with pic16f877a...i want to display frequency via UART but its not working ...this is my code

/*
 * SIMPLE SERIAL FREQUENCY METER
 *
 * this program writes one time per second to the RS232 communication line,
 * the frequency of the input signal on the RB0 pin
 *
 * PIC16F877A
 * 4 Mhz crystal, XT clock
 *
 * PORTB.0, in : counter input
 * PORTc.6, out : RS232 tx
 * PORTc.7, in : RS232 rx

 */

sbit BUZZER at RC1_bit;                 // Buzzer connections
sbit BUZZER_Direction at TRISC1_bit;



/*
 * RAM variables
 */
unsigned long   cntr ;          // number of RB0 transition
unsigned int    ovrflw ;        // number of timer0 overflows
unsigned char   str[10] ;       // display result string

/*
 * constant strings
 */
const unsigned char welcome[] = "\r\rRS232 Frequency Meter Ready" ;
const unsigned char unit[] = " Hz\r" ;

/*
 * write the s ram string to RS232
 */
void    Comm_Write(unsigned char *s)
        {
        while(*s)
                {
                Soft_Uart_Write(*s) ;
                s++ ;
                }
        }

/*
 * write the s constant string to RS232
 */
void    Comm_WriteConst(const unsigned char *s)
        {
        while(*s)
                {
                Soft_Uart_Write(*s) ;
                s++ ;
                }
        }

/*
 * convert the cnrt long value to string
 */
void    Long2str(void)
        {
        unsigned char   i, j ;

        if(cntr == 0)
                {
                str[0] = '0' ;
                str[1] = 0 ;
                }
        else
                {
                str[0] = 0 ;
                i = 0 ;
                while(cntr > 0)
                        {
                        for(j = i + 1 ; j > 0 ; j--)
                                {
                                str[j] = str[j - 1] ;
                                }
                        str[0] = cntr % 10 ;
                        str[0] += '0' ;
                        i++ ;
                        cntr /= 10 ;
                        }
                }
        }

/*
 * interrupt routine called 4000000/256 times by seconds :
 * the timer TMR0 is increased each 4 clock cycles (quartz frequency is 16 Mhz),
 * and overflows when reseting from 255 to 0,
 * calling the interrupt procedure with bit T0IF set
 *
 * also called on each RBO transition, with bit INTF set
 */
void    interrupt(void)
        {
        if(INTCON.INTF)
                {
                /*
                 * RB0 interrupt
                 */
                cntr++ ;                // inc. transition counter
                INTCON.INTF = 0 ;       // clear interrupt flag to enable next call
                }
        else if(INTCON.T0IF)
                {
                /*
                 * TIMER 0 overflow
                 */
                ovrflw++ ;              // inc. overflow counter
                INTCON.T0IF = 0 ;       // clear interrupt flag to enable next call on overflow
                }
        }

/*
 * entry point
 */
main()
 {

        Sound_Init(&PORTC,1);
        Sound_Play(1000,100);



        Soft_Uart_Init(PORTC, 7, 6, 9600, 0) ;    // RS232 on PORTC, bits 7 & 6, 38400 bauds
        Comm_WriteConst(welcome) ;              // write welcome message

        TRISB0_bit = 1 ;                  // RB0 interrupt pin as input

   // T0CON = 0b11001000;

        OPTION_REG = 0b01001000 ;       // no prescaler

        /*
         * main loop
         */
        for(;;)
                {
                cntr = 0 ;              // clear counters
                ovrflw = 0 ;

                INTCON = 0b10000110;           // T0IF, INTF and GIE enabled

                while(ovrflw < 3906) ;         // wait 1 second : 15626 = 16 000 000 / 4 / 256, rounded up

                INTCON.GIE = 0 ;                // stop all interrupts

                Long2Str() ;                    // convert counter to string
                Comm_Write(str) ;               // write string
                Comm_WriteConst(unit) ;         // write unit
                }
  }

//

 

[paulfjujo]

hello



What is your problem ?
Does "Welcome" message appears on your terminal ?
or probelme on interrupts..

what about T0IE_bit and TMR0IE_bit ?

 

[RAJPUT VIDISHA]

HI...
i am getting 0x00 0x00 thats it...sorry i am new to pic device..plz help me

 

[paulfjujo]

why do you not use

unsigned long jj = 3700000;
char txt[11];
...
LongWordToStr(jj, txt);
// txt is "   3700000" (three blanks here)

and UART Hardware ...

Try firts to display a long value on terminal..
and further treat Frequency probleme..

 

[venkimeip]

Hi ,
If you are not getting welcome msg , then there is a error related to baudrate setting. where are you selecting fuse bits,are you enabling external clock by a separate programmer exclusively ??.

 

[RAJPUT VIDISHA]

Hi...
my baud rate is 9600 and i'm selecting it in UART terminal and not enabling external clock...

 

[pic.programmer]

Hi

I am attaching two versions of Frequency Counters. See if this solves your problem. One is PIC16F877A version which runs at 20 MHz clock and another is PIC18F46K22 version which runs at 4 MHz.

I have only tested in Proteus. Please test it in hardware.

 

[HULK28]

Hello RAJPUT VIDISHA,

Try with this code (and also take in count precedent advices):

/*
 * RAM variables
 */
[COLOR="#FF0000"]volatile[/COLOR] unsigned long   cntr ;          // number of RB0 transition
[COLOR="#FF0000"]volatile[/COLOR] unsigned int    ovrflw ;        // number of timer0 overflows

Regards.
JY