Rotary input mechanism for an electronic device

A watch, comprising:

• an enclosure having an aperture formed in a sidewall of the enclosure;
• an input button having a stem that extends into the aperture;
• a sealing element positioned around the stem and forming a seal between the enclosure and the stem;
• an optical sensor configured to sense an optical characteristic of the stem to detect a rotation of the input button about a longitudinal axis of the stem;
• and
• a switch including a collapsible dome and configured to detect a translation of the input button toward the enclosure, wherein:
• the sealing element is configured to move within the aperture and maintain the seal during both the translation of the input button and the rotation of the input button.

A wearable electronic device, comprising:

• an enclosure defining an aperture and an opening;
• a display at least partially received within the opening;
• an input button extending from an outside of the enclosure, through the aperture, and into an inside of the enclosure;
• an optical sensing element within the enclosure and configured to sense a surface of the input button;
• a switch having a collapsible dome positioned proximate to an end of the input button;
• and
• a sealing element positioned within the aperture and around a portion of the input button, wherein:
• the optical sensing element is operable to track a rotation of the input button about an axis by sensing the surface of the input button;
• the switch is operable to detect a translation of the input button along the axis;
• and
• the sealing element is configured to maintain a seal between the input button and the enclosure during both the rotation of the input button and the translation of the input button.