The latest datasheet says: "The OTG Controller integrates the host controller, device controller, and a master-only
I2C-bus interface to implement OTG dual-role device functionality. The dedicated I2C-bus
interface controls an external OTG transceiver."
The pin function select registers state that the USB_SDA and USB_SCL signals are available only on ports P0.27 and P0.28 respectively, but that these pins are not available on the 80-pin package. The LPC175x chips are only available in the 80-pin package though, so it seems that this functionality is not available for these devices, despite the datasheet saying that it is.
So do these chips have the OTG I2C bus but it's not accessible to the outside world, or is the functionality available on different pins? Or is the datasheet incorrect and they don't actually have the OTG I2C bus interface?