touchwin hmi
I don't know what interface have the touchwin device and what protocol use. But on S7-200 the interface is RS485 with gnd on pin 5 line A(Tx/Rx+) on 8 and line B(Tx/Rx-) on 3. The protocol is Siemens propietary PPI or MPI depending on settings. If your HMI have a RS485 interface and can use these protocols you can easily connect to S7-200. If HMI not support Siemens protocols, there is a possibility to configure the serial port of S7-200 on freeport mode and try to implement by software the protocol supported by your HMI. Not an easy task.