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ADT7420 wrong readback register value

Question asked by ndomblides on Jun 6, 2018
Latest reply on Jun 7, 2018 by ndomblides



I'm using a ADT7420 Temperature converter on i2c bus which does not return correct values when I'm reading registers.


For example, The value returned by the device when I'm reading the ID register ( @ 0x0B ) is 0x11 and the datasheet says that the correct value is 0xCB. The i2c frame, seen on a scope, confirm the 0x11 value, and the frame is correctly configured ( see attached Tek00002 file ) .


As another example, I modified Configuration register ( @ 0x03 ) with 0x5E ( see Tek00003 file ). Both CT and INT Pin switch value, confirming that the register has been modified, but when I read back the configuration register, I get 0x11 ( even in the scope trace - Tek00004 file).


But When I'm reading Temperature register value ( @ 0x00 ), I'm getting a correct value ( around 34°C which is the PCB temperature value ).


Do you have some clues to find why the device does not send correct values ?


Thanks for your Help.