Sending trigger and event markers via USB port

How can I send trigger and event marker signals using PTB from the stimulus presenting laptop (Windows) through the USB port to an external device (Brainvision Actichamp amplifier).
I have a USB to serial DB9 cable to connect the two devices.

Would there be delays or any other concerns using a cable like this?


See your other post for the best answers by @xiangrui and @mariokleiner DAQ Device for EEG-Task experiment set up

The problem you will have is how will you configure this cable to do what you want It is just a generic USB-to-serial, and while PTB’s IOPort will be able to open it, you will need to know which pins are required for your device. For TTLs, from what I remember, IOPort needs to send ‘DTR=1’ or ‘DTR=0’ to toggle the data-ready-line as a pseudo-TTL. But if you want event markers, you would normally send a strobed word which a serial port is not designed to do (unless you know your amp specifically supports the serial protocol [which I heavily doubt], not just uses a 9-pin plug).