Carlos Manuel Rodrigues Machado Autonomic Ubiquitous Computing

The power supply circuit is very simple, as it consists only in a voltage regulator to supply the
microcontroller with +5V from the external +12V dc. The noticeable feature is the capability of the
microcontroller to monitor the voltage level before the regulator stops working. This monitoring helps
the device to determine an imminent power supply shutdown or as a measure of the health of the
external power supply. This information is used to save the device state before the power goes
down.
The Teleswitch device also gives feedback to users by showing the activation of inputs or
outputs with 8 leds positioned near to the respective relays. Other 4 leds are used to show the
correct function of the devices and with combination with 2 buttons the users can alter the
configuration by changing the default binding between local inputs and outputs. The feedback
circuit also has a buzzer which indicates the user, with a soft beep, that the fuse was broken. This
feedback helps the user to understand the state of the device and it can be used for debugging
purposes.
Finally the Teleswitch device hardware is composed by an expansion connector that allows
the connection to other sensors. This expansion is also used as an In Circuit Programming (ISP) for
the microcontroller. For development, there is also available a JTAG connector.
5.4.2 Teleswitch Firmware
The Teleswitch prototype device software was programmed in C language, using a module
structure to implement the different parts of the device firmware. No operating system was used
because that would increase the overhead in the firmware using extra memory and processing
power to execute the specific program. The memory usage in the firmware implemented was
adjusted during the program development, and then defined as a fixed value.
The software processing was divided into 3 priority classes, which allow the distribution of
processing. The processing classes consist in high-priority and timed processing, low-priority but
timed processing and background processing.
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