From c to pbp

[keithdoxey]

Thank you.
I want to test this code with Attached Image.
At port.0 and port.1 must have 38khz and at port.6 must have 19khz

You may get the code to work but I dont see how that schematic is going to work if you are trying to build a stereo encoder for an FM transmitter.

Both audio inputs are labelled as {RIGHT} sorry...R IN L IN {end of edit} instead of right and left and the circuit appears to just chop both inputs up at a rate of 38kHz. Presumably the PIC is outputing the two 38kHz signals out of phase otherwise you may as well use the same signal !!!

FM broadcasts were designed to be Mono compatable so have a mono audio signal (L+R) with a difference signal (L-R) carried on a 38kHz subcarrier.

The 19kHz carrier is to operate the pilot indicator in the receiver and switch on the demux to regenerate the original Left and Right signals from Mono + Side.

http://www.irational.org/sic/radio/tech.html#Stereo

gives a block schematic of a stereo encoder which is totally different from what your schematic seems to do.

[Bruce]

For 38kHz on RB0 & RB1, and 19kHz on RB6, you'll need to modify the delay
routines. This should work for ~38kHz & 19kHz. It's off by a few 100Hz, but
a lot closer than the other version.

 ' For 4MHz use XT_OSC
 @ DEVICE PIC16F84A, XT_OSC,WDT_OFF,PROTECT_OFF,PWRT_ON

 ' For 4MHz use 
 DEFINE OSC 4
 ltime VAR BYTE
 TRISB = 0
 
 GOTO Main
 
PAUSE9:    
ASM
    GOTO $+1 ; 2uS
    GOTO $+1 ; 2uS
    GOTO $+1 ; 2uS
    NOP      ; 1uS
    RETURN   ; 2uS 
ENDASM

PAUSE7:    
ASM
    GOTO $+1 ; 2uS
    GOTO $+1 ; 2uS
    NOP      ; 1uS
    RETURN   ; 2uS 
ENDASM

Main:
   FOR ltime = 0 TO 49 ' 0 TO 49 = 50 loops total
    PORTB.7 = 1
    PAUSE 50
    PORTB.7 = 0
    PAUSE 50
   NEXT ltime

   WHILE 1=1
    PORTB = 1
    CALL PAUSE9 ' CALL = 2uS
    PORTB = 2
    CALL PAUSE9
    PORTB = $41
    CALL PAUSE9
    PORTB = $42
    CALL PAUSE7 ' Compensates for GOTO beginning of WHILE loop
   WEND
   
   END

[savnik]

I have made the pcb and these days i will try if work.

[savnik]

I have made the pcb and these days i will try if work.

Thank you Bruce
I test and work , but it should not all the delays they is same; PAUSE9

Edit: I use the code as you post , without any change.

[Jerson]

The delays shown by Bruce are mistakenly wrong. The original code shows delay_cycles(59) That is delay for 59 cycles. So, by using Bruce's code as a start, you can make the delay for 59 cycles. This will give you the correct timings. Another thing, the oscillator is 20MHz. So, the initial define has to be

define OSC  20000000

cntr    byte    1

delay_cycles59:             ' 2 cycles to get here

asm
         MOVLW  11          ' 1 cycle
         MOVWF  _cntr      ' 1 cycle
loop:  DECFSZ _cntr,F     ' 1 cycles  (3*17+1 = 52)
         GOTO   loop          ' 2 cycles
         nop                    ' 1 cycle
         return                 ' 2 cycles

endasm

The above has a subroutine to give you an exact delay of 59 cycles. You can call the function from PBP like this

         gosub  delay_cycles59

[Bruce]

Per Savniks' original post,

How to change this code to picbasic pro.Also i want to use xtal 4MHZ

I think he's looking for a similar function, but with a 4MHz osc VS 20MHz.

If not, then of course the timing in my example would indeed be wrong.

[savnik]

Per Savniks' original post,
I think he's looking for a similar function, but with a 4MHz osc VS 20MHz.

If not, then of course the timing in my example would indeed be wrong.

Yes , I was looking for a similar function, but with a 4MHz Xtal.