Now managing to get images from an interson probe. USB connection seems flaky as hacked, but maybe that's me pushing hard on it.
In any case, it appears that by default we're getting 128 lines per image, going back and forth.
The usb device is tricky, presents itself as a certain VID/PID, but needs to be programmed before it goes in a "programmed PID" mode. Emulating it, we get access to another device, from which we can control, it seems, most of the commands.
Already identified the "start / stop" ones, including both on motors and electrical pulser.
Now the challenge is to correctly take the beginning and end of a frame.