pca_isr.c

DTMF FSK 在51 上的实现

                                                   
//                                                                           
//   PROGRAM DESCRIPTION: 
//        This are the PCA interrupt service routines, which generate the                                                  
//   tone pulse. The CEX2_isr function is the tone detect routine. there is two 
//   kind of caculation for the tone. The first one is count the pulse in one 
//   fixed period. The another way is timing
//   between two pulse.
//
//   ADDITIONAL DOCUMENTATION:                                               
//         Flow Chart:                                                       
//         Support Doc's:                                                    
//                                                                           
//   INPUTS:                                                                 
//   OUTPUTS:                                                                                                                     
//   SUBROUTINE CALLS:                                                       
//   CALLED BY:  Interrupt entrence in main                                                            
//                                                                           
//   REVISION HISTORY:                                                       
//                                                                           
//   DATE        REVISED BY        DESCRIPTION OF CHANGE                     
// ------------------------------------------------------------------------- 

#include<intrins.h>
#include<reg51f.h>
#include"PCA.h"
#include"CFSK.h"
bit CEX2_first_period;					// first time of the count pulse mode

unsigned char PCA_buf0_high;			// PCA module 0 register high byte buffer
unsigned char PCA_buf0_low; 			// PCA module 0 register low byte buffer
unsigned char PCA_buf1_high;			// PCA module 1 register high byte buffer
unsigned char PCA_buf1_low; 			// PCA module 1 register low byte buffer

unsigned char PCA_capture_count;		// store capture pulse count.

/*
This is the CEX2 interrupt service routine. Called by the main.
*/
void CEX2_isr(void)
{
    unsigned int i;
    if(DTMF_capture_flag)
	{
	    // caculate frequency by pulse count in a fixed period
        if(CEX2_first_period)
	    {
		    // this is the first rasing pulse capture
	        PCA_capture_count=0;
	    	CEX2_first_period=0;
	    }
	    else
	    {
		    // increase the count
	        PCA_capture_count++;
	    }
	}
	else if(CFSK_capture_flag)
	{
	    //caculate 4 cycle's period
	    
	    if(CFSK_edge_counter == 0)
		{
		    // this is the first pulse, do some initialization
			// CFSK_capture_finish = 0;
			current_period=0;
			// first edge have been detected.
		    CFSK_edge_counter = 1;
		}
		else if(CFSK_edge_counter < 2)
		{
		    // accumulate period into the buffer;
		    i = CCAP2H;
			i<<=8;
			i=i+CCAP2L;
			i=i-previous_period;
			current_period+=i;
			// increase the rasing edge counter.
		    CFSK_edge_counter++;
		}
		else
		{
		    // we have get 2 cycles period. let's do something and see what's 
		    // reset flag
			CFSK_edge_counter = 0;
			//caculate the interval period between two PCA interrupt
			i = CCAP2H;
			i<<=8;
			i=i+CCAP2L;
			i=i-previous_period;
			current_period+=i;

			if(CFSK_start_bit)
			{
				// just turn off the PCA when we are receiving the bit of one byte.
				CCAPM2=PCA_OFF;
				
			}
			else if((0x3bc<current_period)&&(current_period<0x40E))
			{//
			    //start bit detected here;up limit 2125hz, low limit 1925hz
		    	//received bit is 0:2070HZ
				// start bit is detected here, set the flag bit;
				CFSK_start_bit=1;
				CFSK_bit_counter=0;
				CFSK_received_byte=0;
				CCAPM2 = PCA_OFF;

				// set the sample point in the middle of the next bit.
				TH2=0Xf6;//0XF6-F0
				TL2=0Xe0;
				TR2=1;
				TF2=0;
				ET2=1;
				// the start bit have been detected and next interrupt will enable 
				// PCA capture module.
			}
		}
		//update the previous period buffer with current time point;
		previous_period = CCAP2H;
		previous_period<<=8;
		previous_period+= CCAP2L;
	}
}
/*
This is the CEX0 interrupt service routine. Called by the main. 
This routine generate the high freqency tone.
*/
void CEX0_isr(void)
{   
    //----------------------pin CEX0 interrupt serviece routine
    //reverse the Pin CEX0 status
	CEX0 = ~CEX0;
	//add the period low byte.
	CCAP0L += PCA_buf0_low;
    //add the period high byte.
	if(CY)
    {
    	CCAP0H += PCA_buf0_high;
    	CCAP0H++;
    }
	else
	{
        CCAP0H += PCA_buf0_high;
    }
	// so after a period the interrupt will hapen again.
}
/*
This is the CEX1 interrupt service routine. Called by the main. 
This routine generate the low freqency tone.
*/
void CEX1_isr(void)
{//pin CEX1 interrupt serviece routine
    CEX1 = ~CEX1;
	CCAP1L += PCA_buf1_low;
	if(CY)
	{
	    CCAP1H += PCA_buf1_high;
		CCAP1H++;
	}
	else
	{
	    CCAP1H += PCA_buf1_high;
	}
}