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Programming of AD9880 auto-offset function

Question asked by IgorK on Mar 5, 2014
Latest reply on Mar 12, 2014 by raymondcarter

Customer has a problem to get the auto-offset function working properly.

If once, after plugging in the video signal plug, the offset is wrong, it seems the part never recovers to the correct value. Thus the color gets displayed incorrect.

 

Register 0x1C is written with the value 0x8F.

If customer writes the value 0xCF into the register, the color approaches the correct value. Unfortunately this setting does not always work properly.

The auto-offset starts correctly, but stops before the offset is fully settled to the final (correct) value, which means a certain color offset maintains.

When disabling the post filter (clearing bit 0x1C), the picture appears with correct color matching. Enabling the bit again leads to a color offset again.

 

What may go wrong with the setting?

What may have the post filter acting this (unexpected) way?

What issues may they expect when working without post filter?

Any suggestion how to solve this problem?

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