# SX Specific IR to RS232 routine

```for Sony and the code for 4MHz in PIC compatibility mode
written with CC5XFree follows. see if u can figure it :-)

Rewritten by James Newton for the SX: UNTESTED!!!

//=============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)
* james at sxlist.com
* use CC1B for SX (LST)
*/

/*
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:
. 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+800  = 25+50 = 75
400+1400 = 25+87 = 112
mean ~= (112-75)/2+75 = 18+75 = 93
*/

#define         _sx28_
#include        <sx28.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

#ifdef _sx28_
unsigned char x,y;
bank0	unsigned char r[4];
bank0	unsigned char med,min,max,rxBuf;
bank1	unsigned char buff[16];
bank2	unsigned char buff2[16];
#else
unsigned char x,y,med,min,max,rxBuf;
unsigned char r[4];
unsigned char buff[16];
unsigned char buff2[16];
#endif

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();

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
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
#endif

#ifdef _sx28_
#pragma config &= 0b11010011 // reg 1 = RTCC, no int on RTCC, RTCC internal, prescale, 1:16
PORTA   = 0;
PORTB   = 0;
DDRA = DEF_TRISA;
DDRA = DEF_TRISB;
PA0 = 0;
PA1 = 0;
PA2 = 0;
#endif

#ifdef _16f84_
INTCON  = 0;                                    // no interrupts
PCLATH  = 0;                                    // bank 0
PORTA   = 0;
PORTB   = 0;
TRISA   = DEF_TRISA;
TRISB   = DEF_TRISB;
RP0     = 1;                                    // RAM bank 1
RP0     = 0;                                    // RAM bank 0
#endif

while (1)
{
/* set vars to start */
min  = 255;                             // min period
max  = 0;                               // max period

y    = 0;                               // pointer to buffer
x    = 12;                              // only 12 bits

/* 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
{
//                        buff[y] = 0;
//                        buff2[y] = 0;
/* measure high pulse */
while (TMR0==0);                // wait TMR0 advance
while (IR_input==1)             // wait for 0
{
if (TMR0==0)            // timer overflow (4096us) ?
goto	frame_end	; // yes, exit
}
buff[y] = TMR0;                 // store period
med = TMR0;                     // save high period
TMR0 = 0;                       // start counter

/* measure low pulse */

while (TMR0==0);                // wait TMR0 advance
while (IR_input==0);            // wait for 1
buff2[y] = TMR0;                // store period
med += TMR0;                    // total period
TMR0 = 0;                       // start counter
if (med>=max) max = med;        // find max
if (med<min)  min = med;        // find min

y++;                            // bump pointer
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;

x = y;	//save the size
do
{
Carry = 0;
r[3] = rl(r[3]);
r[2] = rl(r[2]);
r[1] = rl(r[1]);
r[0] = rl(r[0]);
y--;
max = buff[y];
max += buff2[y];
if (max>=med) r[3]++;
} while (y);

/* now r[0],r[1],r[2], r[3] has the frame */
/* Tx the periods and the encoded word */

TxHexAscii(x*2);	//size
TxSerial(0x20);
TxHexAscii(med);
TxEnter();

for(y=0;y<x; y++) {
TxHexAscii(buff[y]);
TxHexAscii(buff2[y]);
TxSerial(0x20);
}
TxEnter();

TxHexAscii(r[0]);
TxHexAscii(r[1]);
TxHexAscii(r[2]);
TxHexAscii(r[3]);

TxEnter();
LED = 0;
}
}

```

 file: /Techref/scenix/lib/io/osi2/ir/irtoserial_sx.htm, 11KB, , updated: 2002/10/25 18:03, local time: 2022/1/22 12:36, TOP NEW HELP FIND:  3.87.250.158:LOG IN

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