S7 Ethernet message to Cognex 5100

If iam not completly mistaken i think that its easier with Controllogix because cognex suports there Ethernet/IP protocol. Siemens does not suport this protocol so you have to use a regular tcp/ip connection

There is a diffrence in how you set up connections depending on if you have a Cp343 ethernetcard or if you are using a Profinetcpu with a built in interface. If you are using a cp card then you need to set up a TCP connection using netpro and use AG_Send to send the commands to the camera.

Cognex supports "TCP" whatever that means exactly, and also "Modbus TCP".
There are some function blocks for CP343-1 and CP443-1 that will let an S7 speak Modbus TCP:
http://www.industry.siemens.com/IT4Industry/en/solution_services/SIMATIC_Addons/proto_mod.htm
If you go this way, please tell me what these blocks cost.

If the above is not possible for you, then exchange the camera for one that supports Profibus or Profinet !

Are you sure you want the network trigger? It is not awfully fast, the overall response time may depend on network traffic. Cognex 5000 series camera has one discrete input and two discrete outputs; that can be expanded, if needed, by purchasing a $500 I/O expansion module.

IMHO, camera trigger and done signals better be real I/O. Reading/writing the inspection data is a different matter: as it was mentioned above, Cognex would respond to standard Modbus commands (function codes H03 and H10), up to 120 cells at a time. The beauty of it - no programming on Cognex side is required (if you need to write data into a cell, you need to put an Integer Edit function in it). The downside is - you cannot change the default Modbus port 502. Also, you should have at least 100 ms time available for data exchange.

I am sure Siemens must have a standard Modbus TCP library.