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ADV7842 I2C Not Working

Question asked by DRC on Apr 29, 2011
Latest reply on Feb 17, 2014 by mattp



I'm not able to communicate with the ADV7842 over the main I2C port to verify that the chip is up and running.  The chip is not ACK'ing the slave address being transmitted.  I've verified on a scope that I am transmitting address 0x40 with the correct START condition (ie. the I2C protocol part looks fine).


I checked all the power supplies, verified the chip is not being held in reset (pulled high), verified the PWRDN1 pin is pulled high. 


I verified that the crystal is oscillating.  The amplitudes I measured are about 2.2V on XTALN and 1.2V on XTALP.  I don't know if this is correct.


I realized that I left the TEST5 pin floating but the HW manual says to connect it to ground in the Pin Description section.  Could this be the problem?

By the way, the HW manual also says to float TEST5 in the Unused Pins section -- this is what caused the confusion, so please correct this in the next revision.


Please let me know what you think and if there's anything else I should verify.