User Notes for HHSC-2x1-FP-3 Foot Pedals

Unpacking, Mechanical details

The pedals are shipped on a white plastic plate 16" wide x 10" deep (40 cm x 25 cm), with the moving pedal components centered around the midline, separated by 9" (23 cm). There is room on this plate for the feet to rest and this may be enough to hold the pedals in place well while they are used. Or you may decide not to use this mounting plate and come up with something specific for your needs and your scanner. Please contact us if you would like help with that. In case you want to mount the pedals yourself, here is the mounting hole pattern:

The four hex nuts shown from above are captive 1/4" x 20 nuts.

Assembly

To assemble the pedals for use just press the optical connectors into the holes on the back of each pedal base. The optical bundle connections are labelled L and R, and these labels are positioned to indicate when the connections are fully mated. (Note that each connector has a triangular peak at the top and a flat bottom -- they will only go in when oriented that way.)

The white labels should align with the rear of the pedal base like this:

The left and right connections can be swapped if, for some reason, you prefer the x/y assignment to swap. The connection labelled L with drive the Y joystick axis, and the R one will drive X.

Once these connections are made some care should be used not to bend the connections near the pedal base: high forces there could damage the optical bundle.

Update: We have added a ferrule to provide strain relief to these connections.

These should look like this when the connectors are pushed in fully (note that the peak on the top of these should be vertically up as shown or they won't press in well):

First Tests (with FIU-932 with windows)

Connect the pedals to an FIU-932 interface unit through a removable bundle (BNSC-55-13, BE-17m, or equivalent). Do not do initial testing by connecting the pedals directly to the interface unit -- while that may work it is possible the signals will be too strong and produce confusing results.

The connect the 932 to a computer using the USB cable.

Select AUTOCONFIGURE on the 932. Choose USB HID JOYSTICK.

Open the windows game controller control panel, and click on 'Properties'. Now when you press the pedals you should see well behaved control of X and Y.

If this all works then you are "on the air" and it is time to think about how to collect real data.

Taking Joystick Data

We provide 2 very short python scripts (fp_test.py and fp_stream.py) as examples of how to read the pedal data. They are almost identical, but fp_stream.py writes the data to a file (called fp.dat) so that they can be plotted.

These programs need pygame to be installed on the system in addition to python. It is hoped that they are short enough to be clear but please get in touch if you want help with them.

In both programs, pressing the 'q' key on a keyboard will quit the program.

If the USB device is not connected the program will quit right away.

Taking Keypress Data

From the root menu, select AUTOCONFIGURE on the 932. Choose USB HID NAR 12345. Now, when the right pedal is pressed a USB HID keyboard '1' will be sent, and when the left pedal is pressed a '2' will be sent. If the pedals are held down the keypresses will be auto-repeated.

Recommendations for Comfortable Use

To provide comfortable use to the subject and minimize motion artifact we recommend:

• Leg bent at knee 10° - 20°, with cushion under knee
• 2nd cushion support under lower leg near ankle permitting foot to move without upper leg movement
• Heel as close as possible to bed but not touching
• Pedal in contact with ball or sole of foot with foot held back slightly from resting position

The foot should slide on the pedal when the foot is pressed forward so socks are preferable to frictional shoe surfaces.

The pedals are intentionally curved to aid in the sliding action -- if you attempt to position the foot so it is flat on the pedal face the result will probably not be very ergonomic for the subject.

If the ankle support can be placed on the mounting plate that holds the pedal, it should serve to keep the pedals in place.