when I say driver then it is ALWAYS the AS1300
Yeah well...when I say 'driver' it depends on the context. It could be a chip, it could be software.
the postman was at your message box
I've just spent 10 mins looking at your schematic and the first 3 things that come to mind are:
1) 100K pullups on SCL and SDA are far too high. Increasing the resistance tends to reduce the effective length of the bus and the bus speed
2) Even though we had a discussion about it which you took part in....you don't have pin 18 connected to VDD so the chips won't work.
3) Are you absolutely sure that the multiplexers are selecting the correct addresses for each of the chips. Don't just say yes...read with a meter the resistance connected to the ADDR pin AT THE PIN of each chip.
You may have 2 resistors in parallel or have the wrong ones selected.
You could also scan the whole address range in software to see if you get an ack.
proof of 2)
from binarygodand thanks for the information about the VDD pin!!
Rectify these and then we'll see what happens.