The decay of coherently prepared excited triplet state can be observed by pulse optically detected magnetic resonance (ODMR). Analysis of this data yields important information about the various relaxation pathways open to a molecule in a given environment. Pulse ODMR requires shorter pulses with higher resolution than those used in pulse nuclear magnetic resonance. Programmable pulse train generators are commercially available, but they can be costly. In this article, a fully programmable photon counter‐pulse train generator interface is described which has the required resolution and speed. The interface cards occupy two slots of a personal computer and are based on advanced Shottky transistor–transistor logic series of logic circuits. This inexpensive, yet highly flexible apparatus for use in pulse ODMR, can be adapted for other applications, such as pulse magnetic resonance and photon counting. In addition, the modular design allows easy expansion to multichannel pulse or photon counting and to the generation of even the most imaginative pulse sequences.