Using DRIVE-3 with the BIRCH-OIU

1. Turn on the Birch interface unit

Connect the power supply: Note that there is a flat side on the power connector and this should face towards the front panel touch screen. The connector should click into place.

Push in the black button to the left of the power supply connection to turn it on.

It will take about 30 seconds for the device to be ready to use.

It is best to leave Birch on at all times to achieve minimum analog drift. While the device is warming up you may observe baseline shifts (changes in the resting outputs over time) from the foot pedals because these are inherently analog: these drifts will be minimized by leaving Birch powered up.

2. Connect the DRIVE-3 optics to the Birch interface unit

Connect the BN-D3 bundle from the driving components to the bundle extension (BE-17m or similar). Then connect the bundle extension to the Birch 12-way optical connector.

3. Choose the mode and do basic tests

Tap on the 'hand' image to choose the response device and then choose 'Automatically': after a few seconds you should see "We detected DRIVE-3. Is that right?" -- Tap Yes to confirm. If Birch does not automatically detect the DRIVE-3 device it may mean there is an optical problem, so in that case please check the optical connections from step 1.

Now that the device has been selected, choose an output mode by tapping on the lower left button. Do this with the pedals at rest (feet off!) and the steering wheel centered. There is only one mode option at this time for DRIVE-3 ("HID_DRIVE_JOY" - an HID joystick output mode), so select that one.

A popup will show "Please leave the steering wheel centered for a moment" -- when that goes away give the steering wheel a few quick turns left and right to show the interface unit what range of signals to expect. (The steering position is detected using a reflective quadrature shaft encoder. So what the interface unit "sees" are alternating reflective and non-reflective bands. When you turn the steering wheel back and forth the interface unit adjusts the gain on its inputs to set the alternating bands to good working levels. There is a third "index" channel which is reflective when the wheel is very near zero and non-reflective at all other positions.)

Now check these 4 'vitals':

1. the small vertical bar in the square display is centered when the wheel is centered,
2. that it moves to the right when the wheel is turned clockwise, and vice versa,
3. that the small dot in that display moves up when pressing the gas pedal, and to the left when pressing the brake
4. when the wheel is turned away from the centered position the 'Index' indicator should light up

If any of these are not quite right please see Troubleshooting.

4. Numerical Tests

Using the on-screen indicators check the output signals against these recent measured values:

Steering:

CCW	Centered	CW
225	512	793

Gas and Brake:

Rest	Fully Pressed
498	0

A very useful measure of system health is the gain values for the active channels. They are numbers in the 0 to 30 range where each step corresponds to a gain increase of 2 dB. The interface unit sets the gains by measuring the insertion losses for each channel when the operating mode is selected, so higher gain values are a sign that optical losses are higher. The gains are checked by tapping on the 'Hardware Info' choice in the "hamburger" menu. A recent DRIVE-3 system had these gains (these are only a rough guide):

Gains:

I	Q	-	-	Gas	Index	Brake	-
18	15	0	0	7	6	12	0

When you first install your system it is a very good idea to make a record of these gain values so that you can later check if they are changing significantly.

4. Connect the USB cable and check with software

If the above tests look ok with your system you can go ahead and connect to your computer by USB.

You may want to use the windows game controller control panel to verify the USB connection qualitatively.

This is a python script which displays the Steering, gas, and brake values: drive3_test.py. It requires pygame and has been tested in linux and windows

Troubleshooting

Detection of the gains for the steering wheel shaft encoder occasionally fails. This seems to be related to the speed of turning of turning the wheel and, specifically, seems more likely to happen if the wheel is turned very slowly. Turning it about 1/4 turn CW and CCW, at about a 1 second period, seems like a reliable approach. So, if the steering wheel indicator is not behaving as described above, please quit the operating mode (by tapping on the DRIVE-3 image, and selecting the 3rd option "None: choose to pause response collection") and then re-select the device and the operating mode.

If the steering wheel behavior is not resolved after this, restart the Birch interface.

If the other channels (gas, brake, or index) are not working it probably indicates that one of these was the case during the calibration:

• the pedals were not at rest,
• the steering wheel was not centered