A card reader includes a body, the body being configured for coupling with a device, the device including a device light sensor and a device light source; a reader light sensor that is configured to capture light being emitted from the device light source, wherein, when the body is coupled to the user device, the reader light sensor is positioned adjacent to the device light source; a reader light source that is configured to emit light to the device light sensor, wherein, when the body is coupled to the user device, the reader light source is positioned adjacent to the device light sensor; a reader interface positioned in the body and configured to read the card; and circuitry configured to communicate data between the card reader and the user device using the reader light sensor and the reader light source.