Datasheet

Jon Waddington
11
for a microcontroller to control the display.
The Parallax Propeller is a microcontroller which contains an internal font ROM and is
capable of generating PAL and NTSC video signals [18]. The Propeller contains 8
processors, called cogs, which means that the video signal can be generated by a cog
while the rest of the Propeller can manage the user interface.
The Parallax Propeller was chosen to be the central component of the Information
System due to its video capabilities.
2.7 Radio Transmission
A method of transmitting information wirelessly must be used to transmit the external
temperature to the Information System. There are two main technologies relevant to this
purpose, ZigBee and Bluetooth.
Bluetooth is generally focused on the connection between mobile phones, laptops and
PDAs, etc. Therefore, the data rate is high, dealing with large packets of data. Since the
technology is based on devices with rechargeable batteries, the power consumption is
fairly high [19].
ZigBee is generally used for control and automation. The data rate is lower and it deals
with small packets of data. The aim of ZigBee is to allow the unit to work for months to
years on a single set of batteries [19]. Digi International produces Xbee modules which
use the ZigBee protocol [20]. This technology was chosen as the method of transmitting
the external temperature in Information System.