;
; ***************************************************************************
; ***  Bubble Software Parallax to PIC Source Converter. Copyright 1999.  ***
; ***  http://www.picnpoke.com                 email: sales@picnpoke.com  ***
; ***************************************************************************
;
; SOUND port, pin, frequency, duration
; Generates squarewave tones (notes) of the specified frequency and
; duration. This demonstration program shows how to use lookup tables to
; play tunes or effects from data stored in program memory.

; Device data and reset vector
	P = pic16c55
	#include <16c55.inc>   ; processor assembler definitions
	_CONFIG _xt_osc & _wdt_off & _protect_off
 reset start

 org 8
pin Res d'1' ; Pin number to use as output (0-7).
freq Res d'1' ; Frequency of note.
duratn Res d'1' ; Duration of note.
f_copy Res d'1' ; Copy of freq variable.
temp Res d'1' ; Variable to stretch duratn to 16 bits.
index Res d'1' ; Index to tables of notes, lengths.

 org 0

; Table to convert pin number (0-7) into bit mask (00000001b to 10000000b).
Pinz         ADDWF pcl                  
             RETLW d'1'                 
             RETLW d'2'
             RETLW d'4'
             RETLW d'8'
             RETLW d'16'
             RETLW d'32'
             RETLW d'64'
             RETLW d'128'

; Table of notes for the demonstration tune "Charge."
Notes        ADDWF pcl                  
             RETLW d'166'               
             RETLW d'189'
             RETLW d'204'
             RETLW d'212'
             RETLW d'204'
             RETLW d'212'

; Table of note durations for the demonstration tune "Charge."
Lengths      ADDWF pcl                  
             RETLW d'52'                
             RETLW d'52'
             RETLW d'52'
             RETLW d'82'
             RETLW d'45'
             RETLW d'190'

start        MOVLW d'0'                 ; Output for speaker.
             TRIS 5h
             CLRF temp                  ; Clear LSB of duratn counter.
             CLRF index                 ; Clear the note counter.
start_loop   MOVF index,w               ; Look up note in table.
             CALL Notes                 
             MOVWF freq                 ; Store note in freq.
             MOVF index,w               ; Look up length in table.
             CALL Lengths               
             MOVWF duratn               ; Store in duratn.
             MOVLW d'3'                 ; Select pin 3 of port
             MOVWF pin
             MOVLW d'0'                 ; RA for speaker output
             CALL Sound                 ; Play the sound.
             INCF index                 ; Advance to next sound in tables.
             MOVLW ~d'5'                ; IF index <= 5, play note
             ADDWF index,w
             BTFSS status,c
             GOTO start_loop
             GOTO $                     ; ELSE end.

; Upon entry, the desired speaker pin must already be set up as an output.
; The w register contains a number representing the output port (0-2) for
; RA through RC. Variable "pin" contains the pin number (0-7). The variables
; freq and duratn are the frequency and duration of the note.

; Upon exit, duratn will be cleared to 0, but freq will be intact. If you require the
; value of duratn for some other purpose, copy it before calling Sound. The
; variable pin and the file-select register (fsr) will also have be altered.

Sound        COMF duratn                ; Convert to two's complement.
             INCF duratn                
             MOVWF fsr                  ; Point to the port number.
             MOVLW 5h                   ; Add offset for port RA.
             ADDWF fsr
             MOVF pin,w                 ; Now look up pin number in
             CALL Pinz                  ; table and get bit mask.
             MOVWF pin                  ; Put the mask into pin.
             MOVF freq,w                ; Use copy so freq value is saved.
             MOVWF f_copy
             BTFSC status,z             ; If freq is 0, clear pin to
             CLRF pin                   ; produce a silent delay.
Sound_loop   MOVF pin,w                 ; f_copy=f_copy+1: IF f_copy<=255
             INCFSZ f_copy              ; THEN w=pin ELSE w=0
             CLRW                       ; (makes a silent delay if freq = 0)
             XORWF indirect             ; indirect=indirect XOR w
             MOVF f_copy,w              ; If f_copy has rolled over to 0,
             BTFSC status,z             ; reload it with the value of freq.
             MOVF freq,w                
             MOVWF f_copy               
             INCF temp                  ; Increment LSB of duratn counter.
             BTFSC status,z             ; Overflow? Yes: Increment duratn and
             INCFSZ duratn              ; if it overflows, return. Else loop.
             GOTO Sound_loop            
             RETLW 0h                   

 end
             
             
             end