//Fosc=11.0592MHz    
// states for and variables IR data processing ;    

#include <reg54.h>

typedef enum{     
             IR_idle,     
             IR_waitstart,              
             IR_getaddr,              
             IR_getaddrinv,              
             IR_getdata,              
             IR_getdatainv              
            }_IRstate;                   
   
_IRstate IRstate = IR_idle;    
   
unsigned char IRaddr = 0xff;    
unsigned char _IRaddr = 0xff;    
unsigned char IRdata = 0xff;    
unsigned char _IRdata = 0xff;    
unsigned char IR_repeat = 0;    
unsigned char IR_ready = 0;    
unsigned char IR_poweron = 0;    
//bit ir_done=0;    
// time constants    
unsigned int IRtimer = 0; // IR timeout     
   
//cpu初始化    
void cpu_init(void)    
{    
    TMOD=0X11; 		// T0 and T1 十六位定時                    
    TH0=0xee;  		//fosc=11.0592M,timer=5ms    
    TL0=0x00;     
    TR0=1; 			// run timer 0;    
    TF0=0;    
   
    ET0=1;  		// enable tmr 0 overflow interrupt    
    IT0=1; 			// int0 edge sensitive    
    EX0=1; 			//  enable "int0"    
    EA=1;   		// global interupt enable     
}    
   
//T0中斷    
void tmrint() interrupt 1    
{    
    TH0=0xee;    
    TL0=0x00;     
    if (IRtimer)     	//IR接收超時    
        --IRtimer; 		//     
    else   
    {    
        IRstate=IR_idle;    
//        IR_poweron=0;    
    }    
}    
   
//Fosc=11.0592MHz    
#define msec_12p5  	0x2d00    
#define msec_15  	0x3600    
#define msec_9  	0x2066    
//#define msec_9  0x1066    
#define msec_2p5  	0x900    
#define msec_0p9  	0x33d    
#define msec_1p68  	0x610    
   
   
//void IRint() interrupt 0(void)    
   
//When the IR receive pin goes low and interrupt is generated     
// IR is collected by starting timer 2 in the first falling edge of the pin    
// then on every other falling edge, the timer value is saved and the timer restarted .      
// the captured time is then used to get the IR data     
// a "start of data" is 13.5Msec,a "1" is 2.25Msec,a "0" is 1.12 msec and a "repeat" is 11.25msec.    
// the counter increments at 1.085 Usec    
// I allow a fairly large tolerance to time jitter but there are no false triggers seen.    
   
void IRint() interrupt 0    
{    
    static unsigned char bits;    
    unsigned short time;    
    switch(IRstate)    
    {    
        case IR_idle:    
            TL1=0;    
            TH1=0;    
            TR1=1;    
            IRstate=IR_waitstart;    
            IRtimer=26;    
            break;    
        case IR_waitstart: 									//P2_4=!P2_4;    
            TR1=0;    
            time=TH1;    
            time =(time <<8)+TL1;;    
            TL1=0;    
            TH1=0;    
            TR1=1;    
            if ((time > msec_12p5)&&(time < msec_15)) 		// greater than 12.5Msec & less than 15 msec = start code     
            {        
                IRaddr=0;    
                _IRaddr=0;    
                IRdata=0;    
                _IRdata=0;    
                bits=1;    
                IRstate=IR_getaddr;    
            }    
            else if ((time > msec_9)&&(time <  msec_12p5))	// less than 12.5Msec  and greater than 9 msec =Repeat code     
            {         
                IR_repeat=2;    
                IRstate=IR_idle;    
            }    
            else     
            {           									// to short, bad data just go to idle     
                IRstate=IR_idle;                    
            }                    
            break;    
        case IR_getaddr:    								// P2_4=!P2_4;    
            TR1=0;    
            time=TH1;    
            time =(time <<8)+TL1;;    
            TL1=0;    
            TH1=0;    
            TR1=1;    
            if ((time>msec_2p5)||(time<msec_0p9))			// if  > 2.5msec or shorter than .9Msec bad data , go to idle     
            {       
                IRstate=IR_idle;    
                break;     
            }    
            if (time>msec_1p68)								// greater than 1.68Msec is a 1    
            {          
                IRaddr|= bits;    
            }    
            bits=bits<<1;    
            if (!bits)    
            {    
                IRstate=IR_getaddrinv;                    
                bits=1;    
            }    
            break;                  
        case IR_getaddrinv:  								//P2_4=!P2_4;    
            TR1=0;    
            time=TH1;    
            time =(time <<8)+TL1;;    
            TL1=0;    
            TH1=0;    
            TR1=1;    
            if ((time>msec_2p5)||(time<msec_0p9))			// if  > 2.5msec or shorter than .9Msec bad data , go to idle     
            {       
                IRstate=IR_idle;    
                break;     
            }    
            if (time>msec_1p68)								// greater than 1.68Msec is a 1     
            {         
                _IRaddr|= bits;    
            }    
            bits=bits<<1;    
            if (!bits)    
            {    
                IRstate=IR_getdata;;                    
                bits=1;    
            }    
            break;                  
        case IR_getdata:    
            TR1=0;    
            time=TH1;    
            time =(time <<8)+TL1;;    
            TL1=0;    
            TH1=0;    
            TR1=1;    
            if ((time>msec_2p5)||(time<msec_0p9))			// if  > 2.5msec or shorter than .9Msec bad data , go to idle    
            {        
                IRstate=IR_idle;    
                break;     
            }    
            if (time>msec_1p68)								// greater than 1.68Msec is a 1    
            {          
                IRdata|= bits;    
            }    
            bits=bits<<1;    
            if (!bits)    
            {    
                IRstate=IR_getdatainv;                    
                bits=1;    
            }    
            break;                  
        case IR_getdatainv:    
            TR1=0;    
            time=TH1;    
            time =(time <<8)+TL1;;    
            TL1=0;    
            TH1=0;    
            TR1=1;    
            if ((time>msec_2p5)||(time<msec_0p9)) 			// if  > 2.5msec or shorter than .9Msec bad data , go to idle     
            {       
                IRstate=IR_idle;    
                break;     
            }    
            if (time>msec_1p68)			 					// greater than 1.68Msec is a 1     
            {         
                _IRdata|= bits;    
            }    
            bits=bits<<1;    
            if (!bits)         			// we have it all , now we make sure it is a NEC code from the CHS IR transmitter    
            {                   		// make sure address,~address are correct , data ,~data are correct and address is 0.    
                IR_ready=((IRaddr^_IRaddr)==0xff)&&((IRdata^_IRdata)==0xff)&&(IRaddr==0);    
                if(IR_ready)    
                {    
                    IRstate=IR_idle;    
                }        
            }    
            break;                  
        default:    
            IRstate=IR_idle;    
            break;    
    }    
}    
   
void main(void)    
{    
    cpu_init();    
    while(1)    
    {    
        if(IR_ready)    
        {    
            IR_ready=0;    
            switch(IRdata)    
            {    
                case 0x45:        //1    
                    //your code    
                    break;    
                case 0x44:        //3    
                    //your code    
                    break;    
                case 0x43:       //4    
                    //your code    
                    break;    
                case 0x08:        //prev    
                    //your code    
                    break;    
                case 0x5a:        //next    
                    //your code    
                    break;    
                default:    
                    break;    
  /*       &n bsp;*/  }    
        }    
    }    
}