點　本keil c51程序適用uPC1621/uPC1622及兼容的紅外遙控器芯片,占用外部中斷0和定時器1,以中斷方式解碼,節(jié)省系統(tǒng)資源,以查詢方式檢測遙控信號是否有效.

解碼思路:
　　紅外線經(jīng)一體化接受頭解碼放到后送到單片機的外部中斷0,單片機設置外部中斷下降沿觸發(fā),T0和T1為16位定時器,T0在系統(tǒng)啟動后定時5ms.T1在外部中斷0啟動后開始定時,初值為0,每次在INT0中斷后先讀T1計數(shù)值,并重設初值為0,而且判斷T1的計數(shù)值,


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