For debugging, a 115200 baud serial interface is provided as a ttyACM device:

• Please use screen or minicom to connect to it.
• Use username: root, password root.

Also, there is a untested serial interface on the serial 40-pin header: https://pinout.xyz/pinout/uart

If you want to modify the image content the quick-and-dirty way (not recommended):

• Start with the chroot-to-pi script: https://gist.github.com/htruong/7df502fb60268eeee5bca21ef3e436eb
• Edit /bin/bash to /bin/sh on the chroot /mnt/raspbian /bin/bash line.

Tweaking your camera settings

After you get into the pi by the debugging ttyACM interface, you'll see:

# cat /opt/uvc-webcam/start-webcam.sh
#!/bin/sh


/opt/uvc-webcam/multi-gadget.sh
/usr/bin/v4l2-ctl -c auto_exposure=0
/usr/bin/v4l2-ctl -c auto_exposure_bias=15
/usr/bin/v4l2-ctl -c contrast=0
/usr/bin/v4l2-ctl -c video_bitrate=25000000

/opt/uvc-webcam/uvc-gadget -f1 -s2 -r1  -u /dev/video1 -v /dev/video0

Now, you can change the v4l2 parameters on the fly and preview their effects on your camera output.

To get the list of tweakable parameters:

# /usr/bin/v4l2-ctl -L

This is how I tweaked the settings for V1.1. I think it's possible to squeeze even more performance out of this camera.