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AduM2250 not working

I am communicating over I2C between two PIC24FJ microcontrollers (one as master, one as slave) with the AduM2250 in between them.  My schematic is attached.  My software works fine when i communicate between the two microcontrollers without the AduM2250 between them.  I have the master sending the slave some data and then the master requests a response from the slave.  The problem I am having is that communication from the master to the slave works ok (most of the time all the bytes are transferred correctly, but sometimes the slave misses the interrupt or gets hung up).  The main problem is that the master is not receiving the correct data back from the slave.  I will get the first 2-4 bytes back correctly and then the rest is just garbage (and sometimes I only get garbage).  Also sometimes the slave seems to hang up on the TBF flag not being cleared and then it seems to holding the bus low.  Any ideas on what is going on?  I have side 1 as the master and side 2 as the slave.  

IsolatedI2Ccircuit.pdf
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  • So I had an idea to switch sides of the master and slave, so I wrote a little code to make side 2 the master and side 1 the slave and just send a read and a few characters from side 1 to side 2 and the signals are now looking correct, but I am getting this weird negative going clock on every other transmission.  So basically every 200ms I am sending a read command and 3 bytes of data, and on every other send the clock flips between +3.3V and -3.3V.   Scope shots are attached.  What is causing this??

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  • So I had an idea to switch sides of the master and slave, so I wrote a little code to make side 2 the master and side 1 the slave and just send a read and a few characters from side 1 to side 2 and the signals are now looking correct, but I am getting this weird negative going clock on every other transmission.  So basically every 200ms I am sending a read command and 3 bytes of data, and on every other send the clock flips between +3.3V and -3.3V.   Scope shots are attached.  What is causing this??

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