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AD5274 Production
The AD5272 / AD5274 are single-channel, 1024-/256-position digital rheostats that combine industry leading variable resistor performance with nonvolatile...
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AD5274 on Analog.com

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AD5274 userspace driver

		
	
				

			

									
					    mcarrier
					
							

            
            			
				
									
											
			
			
				
			
			
			    	
			                    
                
				                on Feb 17, 2016 
				
			
			
		

		
		                    	    

        	    
Thread Summary

                The user encountered issues with readback from the AD5274 device when using the Linux driver, specifically with the rdac0, otp0en, and otp0 files. A typo in the driver caused readback errors, and a fix was submitted to the mainline kernel. The otp0 attribute accesses the 50-TP memory for setting the power-on-reset position, and otp0en must be set to 1 before writing to otp0. The rdac0 attribute correctly writes 8-bit values to the device.
                        	    

                
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We are using the ad5274 device to control an LCD contrast pin. I have successfully instantiated the ad5274 linux driver. The driver exposes a couple of files in /sys/bus/i2c/devices/000-02c. The files of note are rdac0, otp0en, and otp0. I can't find any documentation that explains how someone is to use these files to program the ad5274 device. Any help?

			

			
									
		                             
                        

    

                                            
                 D/A Converters (DAC)
                
                                                    
                 data converters
                
                                                    
                 AD5274
                
                                                    
                 Digital Potentiometers (DigiPOT)
                
                                
            

    
    
		


				
				        
        		

			
						
									
												
			
			
                        
                                    
                        
                        
                        
            
			            
						
						
			
			
			
			
		


        
        
        
    
					

			





















	

	

					



			








	
	
	
	



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    •  Analog Employees  
    
            
						
                            
            
            				
            
                on Feb 22, 2016 3:53 AM
            
            
						
			            		
    
		
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    Hi Michael,
    
 
    Sorry for the delay - we tested the AD5272/5274 support using a AD5272 which always worked flawless.
    
 
    In fact there is typo which caused the AD5274 read-back problems.
    
 
    A fix was send mainline:
    
 
    LKML: <michael.hennerich@analog ...: [PATCH] drivers/misc/ad525x_dpot: AD5274 fix RDAC read back errors
    
 
    Testing:
    
 
    root@linaro-ubuntu-desktop:~# cd /sys/bus/i2c/devices/0-002f/
    
 
    root@linaro-ubuntu-desktop:/sys/bus/i2c/devices/0-002f# ls -al
    
 
    total 0
    
 
    drwxr-xr-x 3 root root    0 Jan  1  1970 .
    
 
    drwxr-xr-x 6 root root    0 Jan  1  1970 ..
    
 
    lrwxrwxrwx 1 root root    0 Feb 22 09:36 driver -> ../../../../../../bus/i2c/drivers/ad_dpot
    
 
    -r--r--r-- 1 root root 4096 Feb 22 09:36 modalias
    
 
    -r--r--r-- 1 root root 4096 Feb 22 09:36 name
    
 
    lrwxrwxrwx 1 root root    0 Feb 22 09:36 of_node -> ../../../../../../firmware/devicetree/base/amba/i2c@e0004000/ad5172@2f
    
 
    -rw-r--r-- 1 root root 4096 Feb 22 09:36 otp0
    
 
    -rw-r--r-- 1 root root 4096 Feb 22 09:36 otp0en
    
 
    drwxr-xr-x 2 root root    0 Feb 22 09:36 power
    
 
    -rw-r--r-- 1 root root 4096 Feb 22 09:36 rdac0
    
 
    lrwxrwxrwx 1 root root    0 Jan  1  1970 subsystem -> ../../../../../../bus/i2c
    
 
    -rw-r--r-- 1 root root 4096 Jan  1  1970 uevent
    
 
    root@linaro-ubuntu-desktop:/sys/bus/i2c/devices/0-002f# grep "" *
    
 
    modalias:i2c:ad5274
    
 
    name:ad5274
    
 
    otp0:42
    
 
    otp0en:disabled
    
 
    rdac0:42
    
 
    uevent:DRIVER=ad_dpot
    
 
    uevent:OF_NAME=ad5172
    
 
    uevent:OF_FULLNAME=/amba/i2c@e0004000/ad5172@2f
    
 
    uevent:OF_COMPATIBLE_0=ad5274
    
 
    uevent:OF_COMPATIBLE_N=1
    
 
    uevent:MODALIAS=i2c:ad5274
    
 
    root@linaro-ubuntu-desktop:/sys/bus/i2c/devices/0-002f# for i in `seq 0 255`; do echo $i > rdac0;cat rdac0; done;                                                                                            
    
 
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    root@linaro-ubuntu-desktop:/sys/bus/i2c/devices/0-002f#
    
 
    -Michael
    
			
    

		
			
	      

		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
				
						
						
				
				
		
		
    
			
		
    
	
    

    

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    •  Analog Employees  
    
            
						
                            
            
            				
            
                on Feb 22, 2016 3:53 AM
            
            
						
			            		
    
		
										0
					
	
    

		
		
    
		
    
                                
                                                            
    
					
    Hi Michael,
    
 
    Sorry for the delay - we tested the AD5272/5274 support using a AD5272 which always worked flawless.
    
 
    In fact there is typo which caused the AD5274 read-back problems.
    
 
    A fix was send mainline:
    
 
    LKML: <michael.hennerich@analog ...: [PATCH] drivers/misc/ad525x_dpot: AD5274 fix RDAC read back errors
    
 
    Testing:
    
 
    root@linaro-ubuntu-desktop:~# cd /sys/bus/i2c/devices/0-002f/
    
 
    root@linaro-ubuntu-desktop:/sys/bus/i2c/devices/0-002f# ls -al
    
 
    total 0
    
 
    drwxr-xr-x 3 root root    0 Jan  1  1970 .
    
 
    drwxr-xr-x 6 root root    0 Jan  1  1970 ..
    
 
    lrwxrwxrwx 1 root root    0 Feb 22 09:36 driver -> ../../../../../../bus/i2c/drivers/ad_dpot
    
 
    -r--r--r-- 1 root root 4096 Feb 22 09:36 modalias
    
 
    -r--r--r-- 1 root root 4096 Feb 22 09:36 name
    
 
    lrwxrwxrwx 1 root root    0 Feb 22 09:36 of_node -> ../../../../../../firmware/devicetree/base/amba/i2c@e0004000/ad5172@2f
    
 
    -rw-r--r-- 1 root root 4096 Feb 22 09:36 otp0
    
 
    -rw-r--r-- 1 root root 4096 Feb 22 09:36 otp0en
    
 
    drwxr-xr-x 2 root root    0 Feb 22 09:36 power
    
 
    -rw-r--r-- 1 root root 4096 Feb 22 09:36 rdac0
    
 
    lrwxrwxrwx 1 root root    0 Jan  1  1970 subsystem -> ../../../../../../bus/i2c
    
 
    -rw-r--r-- 1 root root 4096 Jan  1  1970 uevent
    
 
    root@linaro-ubuntu-desktop:/sys/bus/i2c/devices/0-002f# grep "" *
    
 
    modalias:i2c:ad5274
    
 
    name:ad5274
    
 
    otp0:42
    
 
    otp0en:disabled
    
 
    rdac0:42
    
 
    uevent:DRIVER=ad_dpot
    
 
    uevent:OF_NAME=ad5172
    
 
    uevent:OF_FULLNAME=/amba/i2c@e0004000/ad5172@2f
    
 
    uevent:OF_COMPATIBLE_0=ad5274
    
 
    uevent:OF_COMPATIBLE_N=1
    
 
    uevent:MODALIAS=i2c:ad5274
    
 
    root@linaro-ubuntu-desktop:/sys/bus/i2c/devices/0-002f# for i in `seq 0 255`; do echo $i > rdac0;cat rdac0; done;                                                                                            
    
 
    0
    
 
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    [ --snip-- ]
    
 
    240
    
 
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    246
    
 
    247
    
 
    248
    
 
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    root@linaro-ubuntu-desktop:/sys/bus/i2c/devices/0-002f#
    
 
    -Michael
    
			
    

		
			
	      

		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
				
						
						
				
				
		
		
    
			
		
    
	
    

    

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