Knowledge Base

Problem

User has configured EthoVision XT Trial Control to send TTL pulses via the miniUSB I/O box for synchronizing with a fiber photometry system, but the photometry system does not detect any TTL signal. The hardware appears connected and Trial Control settings look correct.

Details

TTL output issues when using the miniUSB I/O box can stem from several causes: the I/O box not being selected in Experiment Settings, the signal duration being too short for the receiving device to register, hardware not being powered before EthoVision launches, or the receiving device itself not being configured to accept TTL input. Applies to EthoVision XT 15 and later with the Trial & Hardware Control module and miniUSB I/O box.

Solution

1. Before launching EthoVision XT, ensure the miniUSB I/O box is connected to the PC and all receiving devices (e.g., fiber photometry system) are powered on.
2. In EthoVision XT, go to Experiment Settings and confirm that 'Use Trial Control hardware' is enabled.
3. Click Settings next to Trial Control hardware and verify that the Noldus Mini USB-IO box is selected as the interface device.
4. Use the Device Configuration / Test function to manually trigger a TTL output and verify the I/O box LED responds.
5. Increase the TTL pulse duration in your Trial Control rule from 0.1 s to 1–2 s and set it to repeat, then test again — some receiving devices require a longer pulse to register.
6. Confirm with the fiber photometry system documentation that it is configured to receive TTL input on the correct port and at the appropriate voltage level (EthoVision I/O box outputs 5V TTL).
7. Check the cable connection between the I/O box TTL output port and the photometry system input — use a BNC or appropriate adapter as required.
8. If pulses are still not detected, connect an oscilloscope or TTL tester to the I/O box output to confirm the signal is physically present before suspecting a software issue.