Sony SIRC IR Issue

[Bruce]

Here's an easier way without hardware PWM. I haven't tested this on a Sony TV, but it
works great for testing our Sony decoders.

@ DEVICE PIC16F648A, xt_osc, wdt_off, mclr_off, lvp_off, protect_off

DEFINE OSC 4

' Sony TV - IR pulse timing
Synch         CON 96   ' 96 x 25uS = 2.4mS (synch pulse with carrier ON)
Interbit      CON 500  ' 500uS (delay between data bits with carrier OFF)
InterPacket   CON 26000' 26mS (delay between data packets with carrier OFF)
Logic1        CON 48   ' 48 x 25uS = 1.2mS. Logic 1 bit = 1.2mS (carrier ON)
Logic0        CON 23   ' 24 x 25uS = 600uS. Logic 0 bit = 600uS (carrier ON)

' Packet format: 7 bits on left are button number. 5 bits on right select TV.
K1      CON %000000010000 ' BUTTON 1
K2      CON %100000010000 ' BUTTON 2
K3      CON %010000010000 ' BUTTON 3
K4      CON %110000010000 ' BUTTON 4
K5      CON %001000010000 ' BUTTON 5
K6      CON %101000010000 ' BUTTON 6
K7      CON %011000010000 ' BUTTON 7
K8      CON %111000010000 ' BUTTON 8
K9      CON %000100010000 ' BUTTON 9
K0      CON %100100010000 ' BUTTON 0
MENU    CON %000000010000 ' MENU BUTTON
MUTE    CON %001010010000 ' MUTE BUTTON
CHUP    CON %000010010000 ' CHANNEL UP BUTTON
CHDWN   CON %100010010000 ' CHANNEL DOWN BUTTON
VOLUP   CON %010010010000 ' VOLUME UP BUTTON
VOLDWN  CON %110010010000 ' VOLUME DOWN BUTTON
PREVCH  CON %110111010000 ' PREVIOUS CHANNEL BUTTON
ENTER   CON %110100010000 ' ENTER BUTTON
POWER   CON %101010010000 ' ON/OFF POWER BUTTON

X        VAR BYTE ' Data bit loop counter & bit index pointer
Duration VAR BYTE ' Duration of button press
Loops    VAR BYTE ' Loop count
Cycles   VAR BYTE BANK0 SYSTEM' Number of carrier cycles to generate
Key      VAR WORD ' Button # to send

PORTB = %00000000       ' All outputs = 0 on boot
TRISB = %00000000       ' RB0 = IRLED out
                        
@ #define IRTX PORTB    ; Define port to use for IR out
@ #define PIN 0         ; Define port pin for IR out

    GOTO Main       ' Jump over pulse routine to Main
    
Pulse:              ' Generate "Cycles" number of 40kHz pulses
ASM                 ; Keep this routine in code page 1, and jump over to Main
   bsf IRTX,PIN     ; 1uS, LED=on
   goto $+1         ; + 2uS = 3uS
   goto $+1         ; + 2uS = 5uS
   goto $+1         ; + 2uS = 7uS
   goto $+1         ; + 2uS = 9uS
   goto $+1         ; + 2uS = 11uS
   goto $+1         ; + 2uS = 13uS   
   bcf IRTX,PIN     ; 1uS, LED=off
   goto $+1         ; + 2uS = 3uS
   goto $+1         ; + 2uS = 5uS
   goto $+1         ; + 2uS = 7uS
   goto $+1         ; + 2uS = 9uS
   decfsz Cycles,f  ; + 1uS = 10S    
   goto _Pulse      ; + 2uS = 12uS
ENDASM
   return           ' Return to caller    
    
Main:
    PAUSE 5000
    Key = POWER     ' Press Power button
    Duration = 2    ' Send it twice
    
    FOR Loops = 1 TO Duration ' Loop 1 to duration
      Cycles = Synch          ' 2.4mS synch (carrier on)
      GOSUB Pulse             ' Send synch
      
      ' Synch done, now do data bits
      FOR X = 11 to 0 STEP-1  ' 12-bits total MSB first
        PAUSEUS InterBit      ' Pause InterBit delay period (carrier off)
        IF Key.0[X] = 1 THEN  ' 
           Cycles = Logic1    ' Logic 1
        ELSE                  ' or
           Cycles = Logic0    ' Logic 0
        ENDIF
        GOSUB Pulse           ' Send data
      NEXT X                  ' Loop for all 12-bits
      
      PAUSEUS InterPacket     ' Inter-Packet delay period (carrier off)
    NEXT Loops                ' Loop for duration
    GOTO Main                 ' Return for more

    END