We use microwave radiation generated by a semiconductor double-quantum-dot (DQD) micromaser for charge-state detection. A cavity is populated with nc∼6000 photons by driving a current through an emitter DQD. These photons are used to sense the charge state of a target DQD that is located at the opposite end of the cavity. The charge dynamics in the target DQD influences the output power and emission frequency of the maser. Three different readout mechanisms are compared. The detection scheme requires no cavity input field and may potentially be used to improve the scalability of semiconductor and superconducting qubit readout technologies.