Lumina 3G to receive GE scanner TTL

Dear all,

We have an fMRI setup that includes a Lumina 3G controller connected to a response pad and a GE scanner. The Lumina 3G controller is to receive the scanner TTL pulses, which will trigger an E-Prime program on a PC (Windows 10 with USB ports only, the driver specified in Cedrus website was installed).

Performing an fMRI scan on the GE scanner didn’t trigger the E-Prime program to start. To troubleshoot, the TTL pulses from the scanner were confirmed and measured by using an oscilloscope. The TTLs were ~2.28 volts with 1 ms duration. During the fMRI scan, I was expecting to see LED on Lumina controller lights up when it received the scanner TTLs. However, no LED lit up for TTLs.

(1) Do I miss any steps in setting up Lumina to detect GE scanner TTLs? Or
(2) the 2.28v of the TTL (whose voltage is lower than commonly-seen 5v TTL) is too low to be detected by Lumina 3G controller? If so, any measure to make it work?

Thank you.

Wen-Tung Wang