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FIR filter in a sample based interrupt configuration



		

			

									
					    khal
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Oct 24, 2011 
				
			
			
		
    

				
		
    
		    		    
		    
		    	
			
    Hi,
    
 
    I have a sharc-21479 EZ-Lite development kit and I am trying to program an FIR of length 1024 which is calculated every sample. My samples are coming at rate of 100KSPS through the SPI bus connected to the ADC. The second SPI bus is connected to the DAC to creat an audio loop-back. I have tested and checked the the loop-back audio routine (i.e. audio in, ADC, sharc-21479, DAC, audio out) works fine. When I am trying to include and FIR calculation which gets called every sample, the system gets stuck for some strange reason. Even if the weights of the filter are just an impulse, I get nothing at the output. Before I went to an interrupt service routine I do the necessary pushes and pops in assembely as follows:
    
 
    push sts;
    
 
    bit set MODE1 SRD1L |SRD1H | SRD2L |SRD2H | SRRFL | SRRFH;
    .......
    
 
    pop sts
    
 
    Baring in mind that I am using assembly all the way through what else do I need to push to gurantee that my status before the interrupt (i.e. when I was calculating my FIR) is maintained after the interrupt has been serviced. When I test the same system with C function (interrupts), I don't have the same problem. I can't use the C interrupt as that takes alot of over head and I want to speed my ISR.
    
 
    Regards
    
 
    Khal