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FSK Demodulation with ADAU 1701



		

			

									
					    Lama
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Jul 8, 2022 
				
			
			
		
    

				
		
    
		    		    
		    
		    		            		        
    Category: Software
    
    		        		            		    
    Product Number:  ADAU 1701 
    
    		        		    		    	
			
    Hi,
    

    I am firmly new to DSP and just verifying, if my application can be fulfilled by ADAU1701. We use this DSP for audio enhancement and signal leveling. Now I am wondering, if it could also demodulate an FSK signal. In this case, we would not need an additional modem IC.
    

    The requirements are really simple: frequency-shift between 1300 Hz and 2100 Hz; Modulation rate of 1200 baud
    

    However, The FSK signal is transmitted along with default speech audio and I need to detect the FSK signal and mute it on one output channel.
    

    I found approach for incoherent filters here. However, I cannot get it to work.
    

    Thanks in  advance.
    
								
    

				
				
		
    
			
						
									
									
						
						
			
			
			
			
		
    

        
        

					
    
			
    


    


	















    
	
    
	
    
					



			








	
	
	
	



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      •  Analog Employees  
      
            
			                            
                        
                on Jul 8, 2022 11:47 PM
            
            
					
      
	
      

		
		
      
					
      Hello Lama,
      

      

      You found the right post with two different ways to demodulate. So you want to mute the audio output when FSK is detected correct? 
      

      Well, the first approach in the post you found is showing a way to do it. The output of the two filters are going through a peak envelop generator. That output can be summed and tested with a threshold level stored in a DC cell using an ABCD block like KJBob did. Then with that signal you invert it and use that to control a volume control. Most of the pieces are there. 
      

      

      So what are you not able to get working? The FSK or the muting?
      

      Feel free to attach your project. It usually saves time so we are not guessing. 
      

      Dave T
      
			
      

		
		
		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

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                on Jul 28, 2022 5:20 PM
            
            
												
						in reply to DaveThib
					
									
        
	
        

		
		
        
					
        After some more days of work on this project, I decided to give up.
        

        I ignore the glitches and I tried to raise the sampling frequency, but no luck. Above 200 Hz it seems to be no more working at all. Seems, 1701 is not suited for this needs.
        
			
        

		
		
		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
						
				
				
		
		
        
			
		
        
	
        

        

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