曼彻斯特编码的接收
接收程序，给大家分享：rxi(){
// this routine gets called every time TMR0 overflows
if(T0IF)//定时器中断程序
{
TMR0 = PERIOD; // 装计时器初值
T0IF = 0; // 清定时器溢出标志
XTMR++; // 外部的系统时钟计时器加1
RFcount++; // 脉冲宽度计数器加1
return;
}
if(RAIF)//端口电平变化中断程序
{
if (RFFull) // 如果接收位满就退出
return;
RFBit = RFIn; // 取样信号接收的值
RAIF = 0;
switch (RFstate) // 当前状态
{
case TRFDATAUP:
switch (RFcount)
{
case 4:
case 5:
case 6:
case 7:
PORTA = PORTA;//启动端口电平中断
break;
case 8:
case 9:
case 10:
case 11:
case 12:
B <<= 1; // rotate
if ( RFBit==0)//如是有效的下跳变则该位的数据值为1,上跳变为0
{
B+=1; // shift in bit
}
if ( ( ++BitCount & 7) == 0)
Bptr++; // advance one byte
if (BitCount == NBIT)
{
RFstate = TRFreset; // finished receiving
RFFull = 1;
}
RFcount=0; //重新记时
PORTA = PORTA;//启动端口电平中断
break;
default://超时或不足则退出接收
RFstate = TRFSYNC; // reset state machine in all other cases
RFcount = 0;
Bptr = 0;
BitCount = 0;
PORTA = PORTA;//启动端口电平中断
}
break;
case TRFSYNC:
if ( RFBit)
{ // rising edge detected+---+ +---..
// | |<-Theader-> |
// +----------------+
if ( ( RFcount < SHORT_HEAD) || ( RFcount >= LONG_HEAD))
{
RFstate = TRFreset;
PORTA = PORTA;//启动端口电平中断
break; // too short/long, no header
}
else
{
RFcount =0; // restart counter
RFstate= TRFDATAUP;
PORTA = PORTA;//启动端口电平中断
}
}
else
{ // still low
RFcount=0;
PORTA = PORTA;//启动端口电平中断
}
break;
case TRFreset:
default:
RFstate = TRFSYNC; // reset state machine in all other cases
RFcount = 0;
Bptr = 0;
BitCount = 0;
PORTA = PORTA;//启动端口电平中断
break;
} // switch
} //电平中断
} // rxi
void InitReceiver()
{
IOCA = 2;
T0IF = 0;
T0IE = 1; // TMR0 overflow interrupt
RAIE = 1; //使能端口电平变化中断
GIE = 1; // enable interrupts
RFstate = TRFreset; // reset state machine in all other cases
RFFull = 0; // start with buffer empty
XTMR = 0; // start extended timer
TMR0 = PERIOD; // 装计时器初值
PORTA = PORTA;//启动端口电平中断
}
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