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AD9957 Recommended for New Designs
The AD9957 functions as a universal I/Q modulator and agile upconverter for communications systems where cost, size, power consumption, and dynamic performance...
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How to write successfully user data to RAM in AD9957

		
	
				

			

									
					    bsalski
					
							

            
            			
				
									
											
			
			
				
			
			
			    	
			                    
                
				                on Dec 5, 2016 
				
			
			
		

		
		                     
				
        		

		    
		    		    
		    			

			    
Hi,

 
It seems that this issue has already been raised at this forum. Unfortunately, even though I tried to follow exactly the suggested steps I couldn't get the data successfully delivered to the memory in AD9957. In particular, I'm not sure how to organize the sequence of signals during RAM loading. I tried as follows:

 
1. CS = low

 
2. Send RAM address (0x16)

 
3. Send N 32-bit words one after another (with I/O_Update issued after each of them)

 
4. CS = high

 
Sometimes, I see that the first bit is changed but all the other are unaffected by the above procedure.

 
I will appreciate any suggestions.

 
Bartek

			

			
									
		                             
                        

    

                                            
                 Quadrature Digital Up Converters (QDUC)
                
                                                    
                 High Speed D/A Converters =30MSPS
                
                                                    
                 ad9957
                
                                
            

    
    
		


				
				        
        		

			
						
									
												
			
			
                        
                                    
                        
                        
                        
            
			            
						
						
			
			
			
			
		


        
        
        
    
					

			





















	

	

					



			








	
	
	
	



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    •  Analog Employees  
    
            
						
                            
            
            				
            
                on Dec 12, 2016 2:04 PM
            
            
						
			            		
    
		
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    I think I may have found a possible problem in your RAM code, but I'm not 100% sure because I'm not privy to all of your code. I am guessing that the function, spi_send_register(x), generates a SPI sequence that formats an instruction byte with the appropriate read/write bit and address followed by the data, x. If so, that is a problem.
    
 
    Writing/reading RAM involves a single instruction byte followed by ALL of the desired RAM content. So, you must build an array of RAM values and send them all together (with a single preceding instruction byte).
    
			
    

		
			
	      

		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
				
						
				
				
		
		
    
			
		
    
	
    

    

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    •  Analog Employees  
    
            
						
                            
            
            				
            
                on Dec 12, 2016 2:04 PM
            
            
						
			            		
    
		
										0
					
	
    

		
		
    
		
    
                                
                                                            
    
					
    I think I may have found a possible problem in your RAM code, but I'm not 100% sure because I'm not privy to all of your code. I am guessing that the function, spi_send_register(x), generates a SPI sequence that formats an instruction byte with the appropriate read/write bit and address followed by the data, x. If so, that is a problem.
    
 
    Writing/reading RAM involves a single instruction byte followed by ALL of the desired RAM content. So, you must build an array of RAM values and send them all together (with a single preceding instruction byte).
    
			
    

		
			
	      

		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
				
						
				
				
		
		
    
			
		
    
	
    

    

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