The University of Vigo is building a reconfigurable platform, capable of controlling different physical processes involving different types of sensors and actuators. My part of this bigger project is to create and test the control logic for a measurement system. The hardware for this system was already developed by another student in a previous work. The hardware consists of a presence detector ( optical sensor), which moves along a straight, horizontal line. The movement is caused by a DC motor, whose turns are converted in linear displacements. The distance between the two edges of an object can be determined from the information provided by the optical sensor and an incremental encoder. There are also two "end of line" detectors (limit switches) available for safety reasons.
The reconfigurable control platform is based on a Digilent Nexys2 board which has a Xilinx Spartan 3E FPGA onboard. The realization of the control logic is done by a SoC (System-On-Chip) implementation. A SoC is an on-chip implementation of an embedded system. In this particular project we use the 8-bit Xilinx PicoBlaze softcore processor with some additional hardware logic that is implemented using VHDL (Very High Speed Integrated Circuit Hardware Description Language). This additional logic must work as a peripheral of the processor. Once I complete its design and validation, the peripheral will be included in the design library of the reconfigurable platform.
I started by writing a code in the assembler pBlazeIDE and implemented the generated rom-form from the assembler into my project at Xilinx ISE. In this way, I made a peripheral that is able to let the measurement system operate as follows. First, the DC motor has to be started externally by a switch on the FPGA so the optical sensor is able to move over the horizontal line. When the sensor detects the presence of the object, the encoder starts counting the rotations. At the end of the object, the sensor stops detecting and the encoder, therefore, stops counting. The number of rotations that the encoder has counted can now be decoded by the FPGA to a measurement unit, length. This value is displayed in millimetre (mm) on the LCD display of the Nexys2 board.
The result of my project is a working concept for measuring the length of a flat object.
If you want to cite this thesis in your own thesis, paper, or report, use this format (APA):
STRAUVEN, H. (2009). FPGA-based system for measuring objects.
Unpublished thesis, Xios, IWT.