According to the datasheet for the ONET8501V there are supposed to be internal pullup resistors on both SCK and SDA.
Is there a chance that there is a datasheet error? Five out of five installed devices have exhibited what appears to be a lack of pullup on SDA.
I've tried an external resistor but still haven't had a successful register write and read-back test.
I've got scope capture images here:
http://imgur.com/GXsvJ2n,lIi7aOP
The first image is a write and the second image is a read. Channel 1 is SDA and channel 2 is SCK.
I'm using an MSP430 to bit-bang i2c. There high with exponential decay on the SDA happens when I change the port (in two operations) from a zero output to a floating input (P4OUT = 1 followed by P4DIR = 0).