TTL signals undetected in BNC in.

napple2525

Hello.

The camera (BFS-U3-50S5C-C: 5.0 MP, 35 FPS, Sony IMX264, color | Teledyne Vision Solutions) is not detecting TTL signals when connected to the Bpod BNCIn.

I can confirm that the pulse is visible on an oscilloscope, but even when the camera acquisition is started, the BNC IN button in the GUI does not turn green.

When testing with the Examples/State Machines/BNCTriggeredStateChange.m, the camera still does not detect the signal even after being turned ON. Additionally, when manually operating BNC1 input from the GUI, it detects a “BNC1 (or 2)High” state when switched OFF, not ON.

Setup Information:
Bpod State Machine r2.5
Purchase date: 2024-08-19
Camera: BFS-U3-50S5C-C: 5.0 MP, 35 FPS, Sony IMX264, color | Teledyne Vision Solutions

Josh

Hello napple2525,

From your issue I'm not sure whether you're trying to detect a TTL from the state machine using the camera, or the opposite - a TTL from the camera, using the state machine.

If the first,
The BNCTriggeredStateChange example does not send out a TTL pulse. It waits for a TTL pulse to arrive at the state machine, and then changes states. The example you're looking for is SquarePulseTrain.

If the second, it's possible that the camera TTL does not supply enough current to drive the BNC input channel's optoisolator. One option is to connect the camera to the 'S' and 'GND' screw terminals of a port interface board, connected by Ethernet cable to a free behavior port on the state machine. Incoming TTLs will generate Port1In and Port1Out events.

I hope this helps,

Josh

napple2525

Josh

Thank you for your response.

I am indeed trying to receive the TTL signal from the camera using Bpod, so it’s the latter case.

The signal output from the camera has the following characteristics:

Non-isolated input/output
Output low current: 25mA
Output high level: 24V
Given these specifications, would it be incompatible with Bpod?

Additionally, all four ports are currently in use. I appreciate the suggestion, but it would be difficult to implement that approach at this time.

Josh

Hello Napple2525,

25mA is more than enough current to drive the optoisolator, but 24V is much too high. You need to drop it to 3.3-5V.
You may be able to use a simple voltage divider, though I'd verify with an oscilloscope to ensure that the slew rate is acceptable for your application.

-Josh

napple2525

Thanks, Josh.

It seems the wiring wasn't done properly. I successfully recognized the TTL signal. Thank you!

~_I have set the TTL signal from the camera to 4.5V and confirmed it using an oscilloscope. However, while a 4.8V signal from a function generator (also verified with the oscilloscope) is recognized, the signal from the camera is not detected.

Could you advise on the next steps I should take to address this issue?~~

Napple2525

Josh

Hello Napple2525,

Unfortunately I don't have a good answer.
Somehow the camera's output is not supplying enough current to drive the optoisolator.
If you're handy with a prototyping breadboard, you can probably set up an n-channel MOSFET and 5V supply to boost the drive signal.

-Josh