OS: Win10 PsychoPy version: 3.1 Standard Standalone?: Yes
What are you trying to achieve?: I am trying to send a signal from my laptop to a device called PowerLab that collects our data. I want the stimulus from the laptop to signal to the device to insert a comment at the start of the test. We are currently using these two cables (USB-PPOPPO-PowerLab digital input) to connect the laptop to Powerlab.
I have read other forums, and downloaded the appropriate driver (inpout32) and placed it into the correct folder. I used “USB Device Viewer” to find the device address and specified this in PsychoPy.
I have noticed that when I unplug and plug in the USB cable to the laptop that the appropriate signal is sent to Powerlab and a comment is dropped. But, when I actually run the experiment to try and output the signal, nothing happens. I assume this means that either the signal cannot be processed by the cables or that PsychoPy is not communicating with the device address.
You are going from a USB connection to a TTL input → this means the inpout32 driver is not needed: That driver is for parallel ports … but you are using USB to output data
The correct way to go from USB to a TTL input would be to have the “USB adapter” emulate a serial port … and then use pyserial or a similar library to send serial data (bytes, i.e., numbers from 0 to 255) to that emulated serial port
The USB to parallel port cable you are using seems to be one “of these cables” that only work with printers … as far as I know, they do not adequately emulate a serial port from which you could then send data
You said you see a signal when un/plugging the cable: This could be due to the power going in and out of the cable … as such I would not take it as a proof that the system works
Solution
Your problem is very common and luckily, there are numerous devices targeted at resolving the problem.
Thanks for the quick response! I don’t have a lot of signal processing experience, so I really appreciate the help.
I googled USB adapter to serial port cables and this was one of the cables that I found. I appreciate you taking the time to list a couple of cables, unfortunately, they are quite expensive.
If the cable I found doesn’t or if there isn’t another one in a similar price range (<$100), then I was wondering if It was possible to send a signal from Powerlab to PsychoPy. We do something similar using an MRI machine, where the MRI machine will output a number which triggers PsychoPy to start.
My point is that given your situation (no parallel or “true” serial port available at your laptop), a “cable” will not be sufficient. The products I listed as examples all contain a microcontroller with a specific software running on there. If you cannot accept the high price, you may consider building your own “adapter”, see for example my post here: EEG Triggers via Labjack: How to do the Parallel Port DB25 connection
I am currently writing up a exhaustive documentation on this matter together with @tstenner … but it’ll take some more months until it’s out.
Hope that helps!
Stefan
PS: I don’t think sending signals from Powerlab to your laptop would work … you’ll have the same problem of missing ports that support some kind of TTL signals
