I'm trying to make an adapter between a parallel port and a device used in psych experiments. The port on the device is a 15pin d-sub connector (2 rows like an old game port, not 3 like a monitor)
I know that pins 1-8 on the 15pin connector are the data and that it runs on TTL logic levels, but the data is supposed to be "inverted." Would that typically mean that a 0 is on and a 1 is off, or would it more probably mean that the least-to-most significant bit order is flipped from the parallel port?
Also, in a version sold by the company for $200, the only additional feature is that it buffers the data because the port can be both input and output. However, if we're only ever using the input function of the port it shouldn't require a data buffer, correct?
I can't really see paying $200 for a part that seems to just be an adapater between two connector types and even in the picture on their website looks like it's just electrical-taped or heatshrinked together.
I'd appreciate any help/opinions.
-Mike