Electronic system for a drug delivery device

A drug delivery device comprising:

• an electronic system including a switch assembly that comprises
• a chassis supporting a printed circuit board assembly (PCBA) which has a distal surface comprising at least a first electrical contact, a second electrical contact, and a third electrical contact,
• a ring having an annular ratchet profile, and
• a first electrically conductive and elastically deformable arm) and a second electrically conductive and elastically deformable arm,
• wherein the chassis is configured to move axially relative to the ring from a first axial position to a second axial position during a first switch operation mode,
• wherein the chassis and the ring are configured such that the ring rotates relative to the chassis during a second switch operation mode,
• wherein the first arm is arranged such that an axial movement of the chassis towards the ring during the first switch operation mode closes an electrical connection between the first electrical contact and the first arm, and
• wherein the ratchet profile of the ring is located facing proximally towards the distal surface of the PCBA such that an actuator guided on the ratchet profile at least during the second switch operation mode elastically deforms the second arm (28, 37, 46, 60) thereby alternately opening and closing an electrical connection between the second electrical contact and the third electrical contact via the second arm;
• a dose setting and drive mechanism configured to perform a dose setting operation for setting a dose to be delivered by the drug delivery device and a dose delivery operation for delivering the set dose, the dose setting and drive mechanism comprising the ring;
• and
• a button module comprising an electronic control unit (110) on the PCBA, a rotary sensor, a communication unit with a wireless communication interface for communicating with another device, and a use detection unit comprising the switch assembly, wherein the electronic control unit is configured to control an operation of the electronic system.