The generation of wave packets with well-defined momentum and energy distribution constitutes an experimental challenge in diverse areas of physics. The excitation of nontrivial states, on different lattice configurations, becomes mandatory nowadays to unveil new and exotic properties. In this work, we propose and demonstrate experimentally a straightforward technique to engineer on-chip wave packets by exploiting the radiation of an atomlike waveguide into a one-dimensional lattice. We show that the radiation modes generated after exciting this pseudoatom can be tuned at desired band energies by simply controlling the on-site properties, such that wave packets with precise quasimomentum can be generated. As a benchmark, we use the wave-packet generator for a precise excitation of the well-known topological edge states of a Su-Schrieffer-Heeger photonic lattice.