Added indication of access to the I2C bus (in fact, access to FRAM) - an LED that lights up when the SCL line is low. The quick-and-dirty approach to connect the LED through a 2 kOhm resistor did not pass at all - there was not a single memory module on the bus - it turned out to be too strong pull-up, although it worked after 4.7 kOhm, but in 7407 there are free pins, so through this buffer it turned out more reliable.

Now the RAM "module" schematic looks like this: