It looks like EPrime can generate serial port markers linked with events in the experimental design, using scripts. You can record EEG data using EmotivPRO software and use either a real or virtual serial port to form a pipeline from EPrime to EmotivPRO. EmotivPRO monitors the serial port connection, and when a byte is detected on the serial channel it is entered directly into the EEG data file, which means you can define up to 255 different marker types which are entered in the MARKER column of the EDF or CSV files saved by EmotivPRO.

In order to use E-prime to send markers to EmotivPRO on the same computer, you'll need to install a third-party application for creating a few virtual serial ports (we call them COM2, COM3, you can choose port number in that software, please note that you should not use COM1). After having 2 virtual serial ports, you connect E-prime to a port and then connect EmotivPRO to another one. After, you can start sending your marker. COM1 will be useful when you send markers from other machines with real serial ports (Machine A installed EmotivPRO and machine B installed and send marker from E-prime). More details about our Serial ports in EmotivPRO can be found here.

Also, EmotivPRO enables you to manually enter markers into the data stream using the keyboard on your computer, or via a serial connection (or virtual serial port), USB port, allowing other applications to deliver stimuli and mark events automatically. Any marker entered will appear in the data stream and on the recording timeline during playback, as well as in the application's exported CSV files alongside other data streams. Additionally, the EmotivPRO software supports the Lab Streaming Layer protocol. The LSL feature is intended to facilitate research activities that require sub-millisecond timing precision and to enable effective two-way communication between EmotivPRO and third-party software and equipment.

More information can be found here

https://emotiv.gitbook.io/emotivpro-v3/lab-streaming-layer-lsl/about 

https://github.com/Emotiv/labstreaminglayer

https://emotiv.gitbook.io/emotivpro-v3/event-markers/baseline-markers 

https://emotiv.gitbook.io/emotivpro-v3/event-markers/serial-port-markers

https://emotiv.gitbook.io/emotivpro-v3/event-markers/keystroke-markers

https://emotiv.gitbook.io/emotivpro-v3/event-markers/usb-markers