The code uses a timer to time the periods between "dots" and "dashes". If the button press is shorter than a threshold value then the program generates a "dot", otherwise it generates a "dash". If the timing is not to your liking then alter the time threshold value in the source code.
See the files section to download the Arduino source code.
Mario Gianota
Arduino Enigma
Shari
Melissa LeBlanc-Williams