According to an embodiment disclosed herein, an interface device to be connected to an external mobile device may comprise: a connector; at least one integrated circuit (IC); a memory for storing firmware for the at least one IC and instructions; and at least one processor configured to execute the stored instructions, wherein the instructions, when executed by the processor, cause the processor to: transmit identification data of the interface device, including data associated with the firmware, to the external mobile device through the connector when the interface device is connected to the external mobile device through the connector; receive firmware update data for the at least one IC, which corresponds to the identification data, from the external mobile device through the connector; verify the integrity of the firmware update data; and update the firmware stored in the memory by using the firmware update data when the integrity of the firmware update data has been verified.