For PCS 7,I suggest developed drivers by SIEMENS.As an sample "PCS7_S7HMOD or PCS 7_V71_S7HMODM3" ,handle the Modbus Master communication with slaves via CP341 on ET200M in an H system. Email the group via "function.blocks.industry@siemens.com" and ask them for more help regarding drivers for your task.

Also you can find a list at IT4industry website and search for S7/PCS 7 drivers.

Hope this helps,
Hamid Hosseini