Interfejs komunikacyjny do rejestracji obrazu i danych z kamery termowizyjnej

W artykule opisano zewnętrzny interfejs komunikacyjny zaprojektowany do przesyłania danych pomiarowych z kamery termowizyjnej opracowanej w Wojskowej Akademii Technicznej. Omówiono opracowaną magistralę szeregową transmitującą dane w standardzie LVDS. Porównano interfejs szeregowy z interfejsem VideoBus zrealizowanym w oparciu o magistralę równoległą. Opisano moduł sterujący transmisją szeregową zaimplementowany w układzie FPGA oraz specjalnie opracowany protokół komunikacyjny.

In this article the external digital interface specially designed for thermographic camera built in Military University of Technology is described. The aim of the article is to illustrate challenges encountered during design process of thermal vision camera interface. This article explains main requirements for interface to transfer Infra-Red digital data and describes the solution which we elaborated basing on Low Voltage Differential Signaling (LVDS) physical layer and signaling scheme. We have built interface using general purpose Serializer / Deserializer (SerDes) interface from National Semiconductor as a physical layer. There are many SerDes configurations with different parallel bus widths, but in order to maintain the smallest possible area occupied by the device in camera and lowest possible power consumption, we decided to use 10bit Serializer / Deserializer couple and transmit 14bit IR data words in two data cycles of LVDS link sequentially. To achieve guaranteed real-time lossless transmission, special protocol was designed. The control logic for serial interface was described in VHDL language and implemented in FPGA structure. Designed link was tested with thermovision camera employing microbolometric detector array with 384x288 pixel resolution and producing 30 frames per second. Tests with specially generated patterns of different resolutions were also performed. Designed digital link fulfill our current needs with surplus consuming less than 100 mW of energy.