This project is for those who always wanted to make their own stopwatch. It’s built using a combination of eight seven segment displays multiplexed together and hence can be control by a fewer number of pins. It’s capable of timing minutes seconds, and even 1/10 of a second. The entire project revolves around a chipKIT Uno32 board. Along with the capability to time, it also has start and stop buttons just like a traditional stop watch. This project uses the millis() function for time keeping. The millis() is a built-in function in Arduino, and so in MPIDE, that returns the number of milliseconds elapsed.
The LedControl library is used in this project to interface the MAX7219-based seven segment LED display with the chipKIT Uno32 board. The stopwatch is started and stopped by pressing the push switch attached to INT0 (pin 38) pin. The INT0 trigger mode is defined as FALLING, which means the interrupt routine is called when the INT0 pin goes from high to low. For those interested in the project the complete schematics along with all parts number and the code with necessary library are available to download from the project website.