S5 - S7 Communication

to tell you the truth, about the L1 Driver I have no clue. If you have serious Problems with it contact the guys from IT4 Industry, they will surely help you as much as possible.

The alternative to the L1 Bus would be the Profibus, surely. You can use either the IM308C or the CP 5431, both is possible. If you like you could even use Ethernet, if you use also a CP on S7 side. So this is possible:

DP Protocol,
use IM308C as DP Master or DP Slave,
use CP 5431 as DP Master, FDL or FMS Master (for FDL or FMS you need an additional CP on S7)

Ethernet,
use a CP 1430 TF or TCP ora CP 143 and on S7 side either a CP 343-1 (ISO and TCP) or CP 343-1 Lean (only TCP).

I hope this could help you a bit. [;)]
Best regards