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AD7383-4 Recommended for New Designs
The 16-bit AD7383-4 and 14-bit AD7384-4 are pin-compatible, quad, simultaneous sampling, high speed, successive approximation register (SAR), analog-to...
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AD7383-4 on Analog.com

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CRC read calculation

		
	
				

			

									
					    Imkakakhel
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Apr 9, 2025 
				
			
			
		
    
		
		                     
				
        		
    
		    
		    		    
    
		      		            		        
    Category: Datasheet/Specs
    
    		        		            		    
    Product Number:  ad7383x, ad7383 
    
    		        		    		    
    
		    		    
		    			
    
			    
    Dear all,
    

    I've been working on figuring out the CRC read calculation for the AD7383-4 ADC. Based on the ADC datasheet, I wrote a MATLAB script for the 32-bit CRC calculation, and it correctly matches the remainder shown in the example (see the attached snapshot).
    

    Since I'm using four 4-channel ADCs, I extended the same logic to handle 64-bit data + 8-bit CRC = 72-bit total. However, when I test this on hardware, the ADC result does not match expectations. Adding the CRC to the 64-bit data should result in a final remainder of zero, but unfortunately, that's not happening.
    

    I'm attaching an ILA scope snapshot that shows all four channels, including the CRC read result. (Note: the output matches the input as I’m applying a 4 mV sine wave.)
    

    I've spent a significant amount of time on this, but things still aren't lining up. I would greatly appreciate any help, suggestions, or leads you might have.
    

    Thank you in advance.


    Hardware result:

     


    MATLAB CALCULATION FOR 32bit example of datasheet:

     

     


    CRC RESULT CALCULATION HW RESULT:

     

     
    

    MATLAB EXTENDED CODE:

    

    

    

    

    

    % Define the polynomial (x^8 + x^2 + x + 1) as 9-bit binary
    

    

    

    poly = uint16(bin2dec('100000111')); % 0x107
    

    


    

    

    

    

    % Original ADC channel data (A, B, C, D)
    

    

    

    data = [hex2dec('3904'), hex2dec('3902'), hex2dec('3900'), hex2dec('38f5')];
    

    

    

    disp('Original Data:'), disp(dec2bin(data, 16));
    

    


    

    

    

    

    % Step 1: Invert ONLY the 8 MSBs of Channel A (data(1))
    

    

    

    msb = bitshift(data(1), -8);
    

    

    

    inverted_msb = bitxor(msb, 255);
    

    

    

    data(1) = bitor(bitshift(uint16(inverted_msb), 8), bitand(data(1), 255));
    

    


    

    

    

    

    disp('Data after MSB inversion (only A inverted):'), disp(dec2bin(data, 16));
    

    


    

    

    

    

    % Step 2: Concatenate 4 data words (64-bit total)
    

    

    

    data_stream = uint64(0);
    

    

    

    for i = 1:length(data)
    

    

    

     data_stream = bitor(bitshift(data_stream, 16), uint64(data(i)));
    

    

    

    end
    

    

    

    disp('Concatenated Data Stream (64-bit):'), disp(dec2bin(data_stream, 64));
    

    


    

    

    

    

    % Step 3: Append 8 zeros to the LSBs (72-bit)
    

    

    

    padded_data_stream = [dec2bin(data_stream, 64), '00000000'];
    

    

    

    disp('Data Stream after Appending 8 Zeros:'), disp(padded_data_stream);
    

    


    

    

    

    

    % Step 4: Perform XOR-based CRC division
    

    

    

    data_bits = padded_data_stream - '0';
    

    

    

    poly_bits = dec2bin(poly, 9) - '0';
    

    


    

    

    

    

    for i = 1:(length(data_bits) - length(poly_bits))
    

    

    

     if data_bits(i) == 1
    

    

    

     data_bits(i:i+length(poly_bits)-1) = xor(data_bits(i:i+length(poly_bits)-1), poly_bits);
    

    

    

     end
    

    

    

    end
    

    


    

    

    

    

    % Step 5: Extract the last 8 bits as CRC
    

    

    

    crc_remainder_bits = data_bits(end-7:end);
    

    

    

    crc_remainder = bin2dec(num2str(crc_remainder_bits));
    

    


    

    

    

    

    fprintf('CRC Remainder (Final CRC): 0x%02X\n', crc_remainder);
    

    

    

    disp('Final CRC Binary:'), disp(crc_remainder_bits);



    

    

    

    

    
			
    
			
									
		                             
                        

    
    
                                            
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