Complex sentence: Both board applications used the same circuit board design but the serial circuitry was excluded from the daughter-boards and dip switches were employed to set a unique ID on each board (primary 0, first daughterboard 1, and so on).
Split into simpler sentences: Both board applications used the same circuit board design but the serial interface circuitry was omitted from the daughter-boards. Dip switches were employed to set a unique ID on each board (primary 0, first daughter-board 1, and so on).