Now I couldn't find a USB jack on this keyboard so I used a midi to usb cable. I don't know the make and model of the cable, I bought it over a decade ago for my old keyboard, but I know it still works because I just tested it on the old keyboard. Pictured below:
The way I have it plugged in is the midi connector on the cable labeled "in" is plugged into the "out" port on the SP-280. I have tried plugging Cable-in to keyboard-in, but it doesn't work at all. The cable-out doesn't seem to do anything no matter where it's plugged in so I either leave it unplugged, or plug it into the keyboard-in slot (I think that's where it's supposed to go, but I'm not sure, I'm not really trying to send signals from out of my computer into my keyboard so I don't think it matters, correct me if I'm wrong).
Anyway, as long as I have the cable-in to the keyboard-out I can use the SP-280 as a controller, but either the note hangs with endless sustain (regardless of whether or not I have the sustain pedal plugged in) or the key doesn't trigger a note to play at all. Has anyone else had this same problem and figured out a way to fix it? I would like to use this keyboard instead of my old keyboard controller.