2.2 SOS Sequence Logic Function Implementation

Before generating the waveforms, a time reference is needed. The dot has a period of 50 ms that translates to a duration of 34x50 = 1700 ms for the entire SOS waveform period. Starting from AVR resources, a symmetrical sequence is much easier to implement. To create this symmetry, the period of the reference clock should be half of the dot period (25 ms).

Figure 2-3. Reference Clock
The process of generating the SOS signal can be split into three parts:
  • Generating the waveform for the letters ‘S’
  • Generating the waveform for the letter ‘O’
  • Combining the waveforms