;;; Simple mono flanger

;;; Author:Daniel Bertrand

;;; Date: May 29,2000

;;; This program is free software; you can redistribute it and/or modify  

;;; it under the terms of the GNU General Public License as published by  

;;; the Free Software Foundation; either version 2 of the License, or     

;;; (at your option) any later version.

;;; References:	

;;; http://www.harmony-central.com/Effects/Articles/Flanging/

;;;  speed( formerly "delta")=2*pi*freq/48000

;;;  this give us our delta value for a specific freq (0.1-0.3Hz is good)

	include "emu_constants.asm"

	name "flanger"

in	IO

out	equ in	

speed	  control  2e-05 , 0 , 1e-4 	; Controls frequency (radians)

delay   control  &7e-3  ,$1600 , 20e-3	; twice (2*) average delay (sec)

width	  control  #0.33  ,0	 ,0.5	; width control 

forward	  control  #1	 ,0      ,#1	; forward mix 

feedback  control  0.3   ,0      ,0.5	; feedback level 

;; sine generator storage spaces:	

sinx  sta  0	

cosx  sta  #0.5

tmp  dyn 	

tmp2 dyn

;;; Two Delay Lines:	

dly   delay  &20e-3		;20msec delay line

write	twrite dly,0		; tram writes

ready	tread dly,0		; tram reads

reada   tread dly,0

;;;The code:	

;;; two opcode sinewave generator (I love this chip!):

	macs  sinx,sinx,speed,cosx

	macs1 cosx,cosx,speed,sinx 

;;; 0.5Asint+0.5:	

	macs tmp,C_2^30,sinx,width

;;; calculate address:

	macs  ready.a,write.a,delay,tmp

;second addresses for interpolation:

;(interesting how the emu engineers decided that $800 wasn't a needed value) 

	macints reada.a,ready.a,C_8,C_256 

;;; output values:		

;;; 0x55 is 00100000 (?)

	macints tmp,C_0,reada.a,C_LSshift; get least significant part of address

	interp tmp2,ready,tmp,reada ;interpolate in-between the two delay line readings

	macs  out,in,tmp2,forward

;;; feedback and write to the delay line:

	macs  write,in,tmp2,feedback

	end