Advances in the field of semiconductor technologies in the last years make possible to develop new types of ionizing radiation detectors. The Medipix2 readout ASIC is an example of such a device. It is the hybrid single photon counting imaging chip (sensor and readout chips are fabricated separately). With an appropriate sensor chip on the top, it can count single X-ray photons, without any noise or dark current, at high fluxes (several Gigaphotons per cm2 per second). It also offers excellent radiation hardness and good position resolution (256×256 pixels, each pixel has a 55×55 µm2 area). To make the Medipix2 imaging chip more portable for specific applications a microprocessor controlled read-out system based on the USB (Universal Serial Bus) interface has been developed. It integrates all necessary detector support into one compact device (75×46 mm2). All power supplies including sensor bias (up to 100 V) are internally derived from the voltage provided by the USB connection.