Gredd> I had the same idea. And even bought all the parts. I then wired the outputs (LEDS) from the 3914 to some transistors which then outputted to the pins on a USB keypad interface. (ie: it pretended to trigger a keypress). Trouble was, the 3914 output rises/falls to the final value. So if the output is LED6, the 3914 will light LED 1...LED2...LED3...LED4...LED5.. then finally stopping at LED6. You can place it in DOT mode, so that it only lights 1 LED at a time, but that still doesnt stop it from lighting the LEDs in order as it makes its way to the final value, therefore triggering all the keypresses along the way
. Perhaps if you put a cap inline with each LED output it would reject any signal with too short "ON" time, but this would be a trial and error design. You would have to find the balance between a proper keypress ON time and the rise/fall sweep ON time or it would ignore your actual output value as well.
In the end I purchased an LCD8/8/8 phidget - has a million more features, easy to program and has a cool little LCD
