Schematics – Second Generation Prototype
The initial prototype used an LCD display targeted for a low–cost digital watch. Testing of the prototype revealed that the larger display should be used for improved readability. Since the design was not meant for mass production, ordering a custom made LCD display was not adequate and the design had to use an industry standard LCD display. The display which was chosen does not use the multiplexed driving scheme and therefore requires a higher number of I/O pins. To match this requirement, the MC68HC908GP32 microcontroller was chosen and later exchanged for pin compatible MC68HC908GT8 which features an internal clock generator unit and does not require an external crystal. The schematic diagram of the redesigned application can be seen under figure.