Fecha de publicación: -- Fuente: Wipo "digitalization" This disclosure relates to the field of electric tool technologies, and specifically discloses a charging device, a battery pack, an external device, and a data transmission system. The charging device includes at least a first digital communication module, a second digital communication module, and a first digital signal terminal and a second digital signal terminal respectively connected to the first digital communication module and the second digital communication module. When the charging device is connected to the battery pack, the charging device can perform digital communication with the battery pack through at least one of the digital communication terminals.