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AD9889 EDID Read Speed

Question asked by cdsteinkuehler on Dec 6, 2013
Latest reply on Dec 12, 2013 by DaveD

We are having problems with the AD9889 reading EDID information from monitors with certain HDMI extender cables and/or repeaters.  We have tracked down the issue to slow rise time on the SCL line cause by the extra capacitance, and reducing the pull-up resistor value on the SCL line fixes communication.  The pull-up value, however, is smaller than allowed by the specification and this "fix" doesn't help with product already in the field.

 

We have other HDMI devices that work perfectly fine with the same cable/repeater setup, the difference is the I2C frequency.  The AD9889 is using an apx. 87 KHz I2C bit rate, while the working solutions (various graphics cards and DVD players) are using 20-40 KHz bit rates.

 

Is there any way to program the DDC I2C timings for the AD9889 and slow down the EDID reads so they will work with longer cables that have high capacitance?

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