Recording TTL inputs

[Vincent Prevosto]

Hi,
I'm using a TTL signal to synchronize data across devices on my setup. My open-ephys acquisition board receives that signal from the open-ephys 8-BNC I/O board. I can access the relevant data in both open-ephys and kwik format, but nothing seems to be recorded. I've tested different with source processors (both native and added), but I can't figure how to properly record that signal. The wiki page (https://open-ephys.atlassian.net/wiki/pages/viewpage.action?pageId=950291 ) doesn't help in that respect. What is the proper way to configure digital inputs recordings, (and perhaps display them in the GUI to see if the signal goes through)?
Thanks for your help. 

[Jakob Voigts]

Hi,

the easiest way to see if the digital input works is to use the LFP viewer module. All inputs that are high should display as a transparent colored region. If you don't see this input, maybe there's something wrong on the hardware side? I'd say check If your HDMI cable is plugged into the TTL in port (closest to the headstage connectors) and if the cable itself works. Sometimes, hdmi cables are 'active', which means that there are signal repeater chips in the connectors - these cables don't work to relay simple 5v signals.

If the signals indeed get to the acquisition board but dont make it to the software, there's a few other things we can check.

I'll also add some info to the wiki - that page was a bit sparse indeed.

best,

jakob

[Vincent Prevosto]

All solved now. Thanks for your inputs and clarifying a few things. I see that you've added explanations to the Digital & Analog I/O wiki page, and a link to the LFP Viewer. That'll be helpful if anyone has similar issues in the future. The other thing that Josh clarified for me, was interpreting recorded data. When calling [data, timestamps, info] = load_open_ephys_data('all_channels.events') in Matlab, the TTL on/off value is not in the 'data' variable (which holds the event channel number), but actually accessed in info.eventId. The timestamps variable naturally holds the TTL timestamp. By the way, one thing that might be confusing to user, is the fact that event channels are counted from 0 to 7 (which makes sense from a C coding perspective), but ther I/O board channels is numbered 1 to8. I know it's a small thing, but some people might be puzzled by that.

[Hindiael Belchior]

Hi guys, let me add a question to this topic... I have faced a problem when I use an Arduino delivering 5V TTL signals to OpenEphys. Actually, I've send one single TTL to only one channel of the aquisition board, but unfortunately all the eight channels simultaneously receive the single input. It would not be an issue if I was using only one TTL, but I'll need to use at least three different TTL channels. Have you ever heard about this problem elsewhere? 

Best,

Hindi