PIC Specific RS232 / IR routine 

for Sony and the code for 16F84@4MHz written with CC5XFree 
follows. see if u can figure it :-) 
//=============cut--here================================= 
/* 
 * IR reception 
 * 05/Sep/1999 JLS & CAE 
 * jls at certi.ufsc.br 
 * cae at certi.ufsc.br 
 * CC5xFree v3.0E (www.bknd.com) 
 */ 
/* 
 Sony Data format: 12 bits 
 Bit zero: 
 400 
 +--+ +... 
 | | | 
 + +---+ 
 800 
 Bit one: 
 400 
 +--+ +... 
 | | | 
 + +------+ 
 1400 
 Frame: 
 400 400 
 --+ +--+ +--+ +--+ 
 | | | | | | | 
 +---2600---+ +---+ +------+ +... 
 800 1400 
 Decoding algorithm: 
 - Detect 2600us pulse, 
 - measure next high pulse as P1 (400us) 
 - measure next low pulse as P2 (800/1400us) 
 - store min(P1) 
 - store max(P2) 
 After all measurements: 
 - calculate mean = (max-min)/2 + min 
 - For all (P1,P2) measured: 
 . Add P1+P2=P3 
 . If P3< mean => bit is zero 
 . If P3>=mean => bit is one 
 Measures with Timer0 & Prescaler:16 
 2600us = 162 
 1400us = 87 
 800us = 50 
 400us = 25 
 400+たす800 =わ 25+たす50 =わ 75 
 400+たす1400 =わ 25+たす87 =わ 112 
 mean ~= (112-75)/2+たす75 =わ 18+たす75 =わ 93 
*/ 
#define _16f84_ 
#include <16f84.h> 
#ifdef _12C508_ 
 bit _TxOUT @ GP0; 
 bit RxD_pin @ GP1; 
 bit IR_input @ GP2; 
#else 
 #define RP0 STATUS.5 
 #pragma update_RP 0 /* OFF */ 
 #define DEF_TRISA 0 
 #define DEF_TRISB 6 
 bit Rele @ PORTA.1; 
 bit IR_input @ PORTB.1; 
 bit RxD_pin @ PORTB.2; 
 bit _TxOUT @ PORTB.3; 
 bit LED @ PORTB.4; 
#endif 
unsigned char size,x,y,med,min,max,rxBuf; 
unsigned char r[4]; 
unsigned char buff[32]; 
void TxSerial (unsigned char txBuf); 
/*--------------------------------------------------------------------------*/ 
void TxEnter (void) { 
/*--------------------------------------------------------------------------*/ 
 TxSerial(0xD); 
 TxSerial(0xA); 
} 
/*--------------------------------------------------------------------------*/ 
void TxHexAscii (unsigned char in) { 
/*--------------------------------------------------------------------------*/ 
 unsigned char Hex; 
 Hex = swap(in); // upper nibble 
 Hex &= 0x0F; 
 if (Hex<10) Hex += 0x30; 
 else Hex += 0x37; 
 TxSerial(Hex); 
 Hex = in & 0x0F; 
 if (Hex<0x0A) Hex += 0x30; 
 else Hex += 0x37; 
 TxSerial(Hex); 
} 
/*--------------------------------------------------------------------------*/ 
void Delay_uSeg (unsigned char timeout) { 
/*--------------------------------------------------------------------------*/ 
 // delay = 3*timeout + 7uS (including call and return) 
 while (1) { 
 timeout--; 
 if (timeout==0) { 
 nop(); 
 nop(); 
 return; 
 } 
 } 
} 
/*--------------------------------------------------------------------------*/ 
void TxSerial (unsigned char txBuf) { 
/*--------------------------------------------------------------------------*/ 
/* 
 ;---------------------------------------------------------------------------* 
 ; Transmit 1 start bit Lo, 8 data bits and 1 stop bit Hi at 9600 bps 
 ; No Parity 
 ; Byte time = 1.040 mS 
 ; Bit time = 104 uS (0.16% erro w/4.00 Mhz Internal RC) 
 ; Input : W = byte to be transmitted 
 ; Output: byte transmitted by serial pin 
 ;---------------------------------------------------------------------------* 
*/ 
 char idx; 
 while (1) 
 { 
 Carry = 0; // start bit 
 for (idx=10; idx; idx--) // 3us 
 { 
 _TxOUT = Carry; // 4us 
 Delay_uSeg(28); // 91us (28*3+7) 
 Carry = 1; // 1us 
 txBuf = rr(txBuf); // 1us 
 nop(); // 1us 
 } // 3us 
 return; 
 } 
} 
/*--------------------------------------------------------------------------*/ 
void RxSerial (void) { 
/*--------------------------------------------------------------------------*/ 
/* 
 ;---------------------------------------------------------------------------* 
 ; Receives 1 start bit Lo, 8 data bits and 1 stop bit Hi at 9600 bps 
 ; No Parity 
 ; Byte time = 1.040 mS 
 ; Bit time = 104 uS (0.16% erro w/4.00 Mhz Internal RC) 
 ; 
 ; False start bit check 
 ; 
 ; Start bit hunting timeout = 4*1.283ms 
 ; 
 ; Input : none 
 ; Output : Carry = 1 => success 
 ; rxBuf = input byte 
 ; Carry = 0 => error (timeout or stop bit=0) 
 ;---------------------------------------------------------------------------* 
*/ 
 char idx; 
 rxBuf = 4; // 5.135 ms timeout 
 idx = 0; 
 while (1) 
 { 
 while (RxD_pin) // input "high" 
 { 
 if ((-- idx)==0) 
 { 
 if ((-- rxBuf)==0) 
 { 
 Carry = 0; 
 return; 
 } 
 } 
 } 
 Delay_uSeg(14); // 1/2 bit delay (14*3+7) 
 if (RxD_pin) 
 continue; // false start bit detection 
 rxBuf = 0x80; // 8 bits counter and reception buffer 
 nop(); 
 nop(); // timming adjustment 
 do 
 { 
 Delay_uSeg(30); // (30*3+7)us 
 Carry = RxD_pin; // bit read 
 rxBuf = rr(rxBuf); // store and count 
 } 
 while (Carry==0); 
 Delay_uSeg(30); // 1 bit delay 
 nop(); // timming adjustment 
 Carry = RxD_pin; // stop bit read 
 return; // 100 us availiable 
 } 
} 
 
/*--------------------------------------------------------------------------*/ 
void main (void) { 
/*--------------------------------------------------------------------------*/ 
#ifdef _12C508_ 
// OSCCAL = W; // OscCal Value - OTP part 
 OSCCAL = 0xB0; // OscCal Value - Windowed part 
 GPIO = 0x00; 
 TRIS = 0x08; // GP3 input 
 OPTION = 0b11000011; // Prescaler Timer0 1:16 
#else 
 INTCON = 0; // no interrupts 
 PCLATH = 0; // bank 0 
 PORTA = 0; 
 PORTB = 0; 
 RP0 = 1; // RAM bank 1 
 TRISA = DEF_TRISA; 
 TRISB = DEF_TRISB; 
 OPTION = 0b11000011; // Prescaler Timer0 1:16 
 RP0 = 0; // RAM bank 0 
#endif 
 while (1) 
 { 
 /* set vars to start */ 
 FSR = buff; // pointer to buffer 
 x = 12; // only 12 bits 
 size = 0; // word size in bits 
 min = 255; // min period 
 max = 0; // max period 
 /* start bit management */ 
 while (IR_input==1); // wait for 0 
 /* 2600us start bit */ 
 while (IR_input==0); // wait for 1 
 TMR0 = 0; // start counter 
 do 
 { 
 /* measure high pulse */ 
 INDF = 0; // period: default to zero 
 while (TMR0==0); // wait TMR0 advance 
 while (IR_input==1) // wait for 0 
 { 
 if (TMR0==0) // timer overflow (4096us) ? 
 goto frame_end; // yes, exit 
 } 
 INDF = TMR0; // store period 
 TMR0 = 0; // start counter 
 med = INDF; // save high period 
 FSR++; // bump pointer 
 INDF = 0; // period: default to zero 
 size++; // inc bit counter 
 /* measure low pulse */ 
 while (TMR0==0); // wait TMR0 advance 
 while (IR_input==0); // wait for 1 
 INDF = TMR0; // store period 
 TMR0 = 0; // start counter 
 med += INDF; // total period 
 if (med>=max) max = med; // find max 
 if (med<min) min = med; // find min 
 FSR++; // bump pointer 
 size++; // inc period counter 
 x--; // dec max bits 
 } 
 while (x); 
frame_end: 
 LED = 1; 
 med = max - min; 
 med /= 2; 
 med += min; 
 r[0] = 0; 
 r[1] = 0; 
 r[2] = 0; 
 r[3] = 0; 
 FSR = buff; 
 FSR += size; 
 x = size/2; 
 do 
 { 
 Carry = 0; 
 r[3] = rl(r[3]); 
 r[2] = rl(r[2]); 
 r[1] = rl(r[1]); 
 r[0] = rl(r[0]); 
 FSR--; 
 max = INDF; 
 FSR--; 
 max += INDF; 
 if (max>=med) r[3]++; 
 } while (--x); 
 /* now r[0],r[1],r[2], r[3] has the frame */ 
 /* Tx the periods and the encoded word */ 
 TxHexAscii(size); 
 TxSerial(0x20); 
 TxHexAscii(med); 
 TxEnter(); 
 for(x=0;x<size; x++) 
 { 
 TxHexAscii(buff[x]); 
 TxSerial(0x20); 
 } 
 TxEnter(); 
 TxHexAscii(r[0]); 
 TxHexAscii(r[1]); 
 TxHexAscii(r[2]); 
 TxHexAscii(r[3]); 
 TxEnter(); 
 LED = 0; 
 } 
}

Code:

file: /Techref/microchip/irtoserial.htm, 16KB, , updated: 2005年1月5日 11:53, local time: 2025年9月1日 08:38, owner: JSAG-e_dgo-898,
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<A HREF="http://techref.massmind.org/techref/microchip/irtoserial.htm"> PIC 16F84 Sony IR to Serial converter</A>
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