Using the Drum with an FIU-904 Interface

First: Connect the drum to the interface unit (either directly or through a bundle extension), then connect the USB cable.

Watch the indicators on the 904 interface -- they should light up from right to left in 4 steps taking about 2 seconds total. While they are lighting up do not touch the drum and make sure it is positioned where it will be during use. (So: if you are running a subject in a scanner, for example, make sure the subject is in position with the drum situated where it will used, and then connect the USB as a last step.)

Second: try a few taps on the drum and make sure the 2nd LED from the left blinks when you hit the drum.

If you are not seeing taps the first thing to do is unplug the USB cable and connect it again. When the USB cable is connected the interface unit sets its gain based on what is "sees" connected.

MIDI output

The firmware for the drum sends a MIDI note when a drum beat is detected. After the beat is detected there is a lockout period during which a second beat will be ignored. At the time of this writing the lockout is set to 40ms. At the end of the lockout period a second note is sent with a velocity of zero -- this ends the note.

Beats are detected optically: light is normally passing through a sensor and gets blocked (partially or fully) when the drum is hit. At the time of this writing beats are detected when the signal, which normally hovers close to 3.5V, drops by 0.1 V. This is a value that can be changed to increase or decrease sensitivity but we have not provided access to this for users yet.

The velocity is sent now as a fixed value, not proportional to how hard the drum was hit. We expect to add a proportional velocity in a later firmware release.

-- BenDugan - 02 Mar 2023