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Trouble Configuring AD7738



		

			

									
					    scarlson
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Nov 18, 2015 
				
			
			
		
    

				
		
    
		    		    
		    
		    	
			
    Hi all,
    
 
    First time poster here, long time chip user.  
    
 
    I'm having some trouble getting my AD7738 to work (I do not have the eval kit).
    
 
    I am not seeing anything on my DOUT.  Below is an view of DOUT, DIN, RDY, and CS.
    
 
    to configure it I am sending in 
    
 
    0x00, 0xFF, 0xFF, 0xFF, 0xFF to reset it and then
    
 
    0x01   IO port register, write
    
 
    0xF0   Configure IO port register
    
 
    0x2F   Channel setup register, AIN7, write
    
 
    0x1C  Configure Channel setup register
    
 
    0x37   Channel conversion time register, AIN7, write
    
 
    0x91   Std. value
    
 
    0x3F   Mode register, write (0x3F)
    
 
    0x38   Continuous conversion, no clamp (0x38)
    
 
    and then 0x4F every time RDY is polled.
    
 

    
 
    but all I see is 0x00 in my rxbuffer, occasionally it goes 0xFF.
    
 
    and the DOUT looks terrible.  I'm at a loss.
    
 
    my pin configurations are also
    
 
    SCLK -> SCLK
    
 
    MCLKIN -> CMOS CLK @ 12MHz
    
 
    MCLKUT -> OPEN
    
 
    CS -> SS
    
 
    RESET -> 5V
    
 
    AVdd -> 5V
    
 
    AINCOM/P0 -> OPEN (is this correct?)
    
 
    SYNC/p1 -> OPEN (is this correct?)
    
 
    AIN0-AIN7 -> AIN7 connected to signal generator
    
 
    MUXOUT(+) -> ADCIN(+)
    
 
    MUXOUT(-) -> ADCIN(-)
    
 
    REFIN(+) -> 2.5V (about.. actually 2.38V)
    
 
    REFIN(-) -> GND
    
 
    AGN -> GND
    
 
    RDY -> ISR set to detect inverted rising edge and send out 0x4F
    
 
    DOUT -> MISO
    
 
    DIN -> MOSI
    
 
    DVdd -> 5V
    
 
    DGND -> GND
    
 
    I attached a graph for my 0x4F polling and for my initial setup.  the DOUT is sporadically working.. leading me to think I may have wired something wrong.  
    
 
    Even more confusing, half the time the rxBuffer ISR won't be triggered and other times it will.. with identical code.
    
 
    Any help at all would be great.  I am new to this chip and its kicking my **** and leaving me scratching my head.
    
 
    thanks in advance,
    
 
    scarlson
    
								
    

				
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