Expansion electronic device and electronic system

An expansion electronic device, adapted to be joined with a primary electronic device and to operate cooperatively, the expansion electronic device comprising:

• a housing, having an assembly surface on a top side thereof and a plurality of individually independent receiving chambers on a bottom side thereof, wherein the assembly surface is configured to join with the primary electronic device, and a first waterproof space is formed by means of structural interference between the assembly surface and the primary electronic device;
• and
• a plurality of functional modules, respectively disposed in the receiving chambers, being individually installed or removed, wherein a second waterproof space is formed by means of structural interference between one of the receiving chambers and the corresponding functional module;
• a circuit board, disposed in the second waterproof space and electrically connected to the plurality of functional modules;
• wherein one of the receiving chambers is provided therein with an enclosed block wall configured to define the second waterproof space, and the enclosed block wall has a third interference structure;
• one of the functional modules comprises a base, and a fourth interference structure configured to generate sealed interference with the third interference structure is provided on a bottom of the base;
• and
• wherein the enclosed block wall has a sidewall that has a through hole in communication with the second waterproof space;
• another of the functional modules is disposed in another of the receiving chambers partitioned by the sidewall, the another of the functional modules has a connection port, the connection port is located in the through hole so as to be electrically connected to the circuit board, and the connection port and the through hole generate sealed interference.