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ADSP21161 EZ-KIT Lite Amplitude Modulation Demo

Analog Devices, Inc.
DSP Division
Three Technology Way
P.O. Box 9106
Norwood, MA 02062

Date Created:	8/15/01

Files contained in this directory:

21161_EZKIT_Lite.ldf		Linker Description File
AM_Modulation.dpj		Visual DSP++ 2.0 Project File
AD1836_reg_init_viaSPORTs.asm	Source for initializing AD1836 codec
AD1852_SPI_init.asm		Source for initializing AD1852 codec
Clear_SPT_regs.asm		Subroutines to clear SPORT1 registers
Init_21161_EZKit.asm		Source for main routine
ISR_table.asm			Interrupt Vector Table
SDRAM_initialization.asm	Initialize External Memory
SPORT02_TDM_Initialization.asm	Initialize SPORTS 0 & 2
SPT0_ISR_1836_Processing.asm	Interrupt Routine for SPT0
AM_Modulation.asm		Source file for subroutine
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CONTENTS

I.	FUNCTION/ALGORITHM DESCRIPTION
II.	IMPLEMENTATION DESCRIPTION
III.	OPERATION DESCRIPTION       


I. FUNCTION/ALGORITHM DESCRIPTION

The basis of this project is the 21161 talkthrough example. A processing subroutine
is inserted into the Talkthrough routine.

II.   IMPLEMENTATION DESCRIPTION

       AM_MODULATION.ASM -AM modulation of using common wavetable                                    
                                                                                                     
		 Developed for the 21161 EZ-KIT Lite Evaluation Board                                          
                                                                                                     
                                                                                                     
       Based on Sec.8.1.3 of Introduction to Signal Processing                                       
       By S. J. Orfanidis - 1996, Prentice-Hall                                                      
       ISBN 0-13-209172-0                                                                            
                                                                                                     
                                                                                                     
       I/O equation #1: y(n) = x(n)*sin(2*pi*fc*t)                                                   
                                                                                                     
                            A(n)=sin(2*PI*fc*t)                                                      
                                  |                                                                  
                                  |                                                                  
                                  |                                                                  
           x(n) ----------------->O---------------> y(n)                                             
                                                                                                     
                                                                                                     
                                                                                                     
       I/O equation #2:  y(n) = A(n)*sin(2*pi*f*t) where A(n) = Aenv * sin(2*pi*fenv*t)              
                                                                                                     
                                 A(n)                                                                
                                  |                                                                  
                                  |                                                                  
                                  |                                                                  
           sin(2*PI*fc*t) ------->O---------------> y(n)                                             

       For each input sample, the sample processing algorithm does the following:                   
            generate the AM carrier, A = sin(2*pi*fc*t)                                                 
            y = A * x , or 
				y = A * sin(2*pi*f*t)                                                       
                                                                  

	Why use frequency modulation?                                                                 
	You can develop complex waveforms with rich sounds for synthesis applications by generating   
	frequency modulated signals, then combine them with other amplitude and frequency modulated   
	signals.                                                                                      

	For more introductory information, visit:
	http://www.harmony-central.com/Effects/effects-explained.html                                                                 
                                                                                                     

III.  OPERATION DESCRIPTION

- Plug in a microphone to Mic In and speakers to Ch 2 (Line Out)on the 21161 Ezkit Lite
- Open the project "AM_Modulation.dpj" in the VisualDSP++ Integrated Development Environment (IDE).
- Under the "Project" menu, select "Build Project".
- Open a ADSP21161 EZ-KIT Lite session in the VisualDSP++ Debugger.
- Load "AM_Modulation.dxe"
- Run the Project and speak into the microphone and hear the generated effect.
- Use the IRQ1 and IRQ2 pushbuttons to change the effect settings.
- Pressing the FLAG3 pushbutton will bypass the audio effect.