It was important to time the communication between the LCD and
the microcontroller. The Micrcontroller must also supply the
clock signal to the LCD driver. The following timing diagram
was used to develop the code that simulate it.
Power consumption and conservation of power was a large
consideration when developing the system. It was important to
take advantage of the external interrupts in the chip. Each
button is connected to a pin on port C. They are also
connected to one external interrupt. In order to achieve this
an AND gate was created using diodes. When a button is pushed
and external interrupt is triggered. This wakes up the chip,
checks what pin is low, or what button caused the interrupt.
The appropriate code is executed and the chip is then placed in
sleep mode until another external interrupt is triggered.