vent inrush current and voltage drop
when attached, thus maintaining a
steady input voltage. Due to the circuit,
the system can be reconfigured without
requiring a reboot of the hardware
(blocks) or the software running on the
The controller board can also control
other devices (such as the servo motor
in the actuator block and the LED controller in the flash block) through the
I2C bus, pulse-width modulation
(PWM), and general-purpose input outputs (GPIO) based on commands it receives from the host device. For example, when an actuator block receives the
command for rotation, the MCU generates the pulse signal needed to drive its
The I2C interface is also useful in
terms of scalability because it is widely
used in the field of embedded systems,
allowing us to add various extra devices
(such as a light sensor, acoustic sensor,
IR sensor, GPS, IMU, and multispectral
light source) to the Cambits set.
Lens blocks and optical attachments.
The lens block includes an identification board with I2C expander device
that can detect the identification number of the lens type itself and an additional optical attachment connected to
the lens (such as soft focus filter, lens
array, and “teleidoscope,” or lens for
creating kaleidoscope-like images). The
optical attachment includes no electrical parts but does have up to three
bumps that push against mechanical
switches on the lens block to generate a
three-bit code the lens block can use to
identify the attachment. The lens block
then sends this information upstream.
Sensor block. The sensor block includes a Point Grey camera board
(BFLY-U3-13S2C-CS) that can produce
1.3-megapixel video in various formats
(such as YUV411 and RGB8) and send
the video upstream as a USB 2.0 data
signal. In designing Cambits, we aimed
to minimize the length of the data signal line and the number of connectors
so as to enable high-frequency
(480Mbps) transmission needed to preserve the integrity of the video.
are able to control various imaging parameters of the sensor board (such as
exposure time and gain) from the host
Mechanical design. As mentioned,
the Cambits blocks attach to each oth-
Figure 5. Cambits software architecture.
Computational Photography Processing
Point Grey SDK
Serial Port Driver
Figure 2. Cambits detachable connector: (a) mechanical assembly and alignment of blocks
using magnets; and (b) electrical connection between blocks using spring-loaded pins that
carry power, data, and control signals.
Figure 3. Tree architecture used to implement Cambits; power flows downstream, data
flows upstream, and control signals are communicated in bucket-brigade fashion.
MCU MCU MCU
Spacer Actuator Sensor Lens OpticalAttachment
Figure 4. The base, actuator, spacer, and sensor blocks include a controller board that
allows a block to communicate with its adjacent blocks.
Upstream interface ( 6 pins)
Downstream interface ( 6 pins)
Downstream interface ( 4 pins)