Hardware Reference
In-Depth Information
The LED matrix
The graphical representation of this project will be a matrix of LEDs that Adafruit has
arranged in a very handy product, and there is no need to for additional components
such as resistors, power circuits, and so on: the box contains all that is required to
start quickly.
You can get more details from their website at
http://www.adafruit.com/
When you receive it, you just need to solder some pins as indicated in the Adafruit
documentation and it's ready to be used. As shown in the presentation, the messages
between the matrix and the BeagleBone Black board use a form of the I2C protocol.
Let's look how it works.
Introducing I2C
Whichever board you use in your projects—Arduino, Raspberry, Mini2440—most of
the time, you need to deal with sensors, components, or devices that "talk" I2C or SPI.
These data buses simplify our coder's life. Indeed, our matrix just need to be managed
with only two signals,
SCL
and
DAT
, to execute all the operations.
Instead of a wire for each function, a communication is specified by Philips on the
two wires with the
protocol
part of the I2C. Fortunately, this happens behind the
scenes, thanks to the I2C Linux driver.
Are you interested in getting more details about the I2C bus?
Check out
http://support.saleae.com/hc/en-us/
Circuit
for an interesting explanation.
Using the driver means that, even though you use the I2C protocol, you never have
to deal with the bus message frames, CRC, and all the detail of the protocol, so you
can focus on the data to be sent from BeagleBone to the matrix.
