Mikrokomputer Raspberry Pi jako sterownik systemu pomiarowego

摘要

In this paper the system based on Raspberry Pi, a popular educational microcomputer is described. In this system, a programmable FPGA Spartan-3 XC3S200 device was tested. The Raspberry Pi worked as a control unit for the whole system (Fig. 1). A part of the system was implemented inside the tested structure (Fig. 2). It was an array of ring oscillators (Fig. 3), as temperature sensors, with a structure for controlling the ring oscillators. Simple ring oscillators are often implemented in FPGA devices. They are used both as a single element or an array of sensors for measuring the chip temperature. The frequency of the activated sensor was measured outside by an oscilloscope (SCPI command was used). The frequency was dependent on temperature. The sensors can be located in different areas of a chip. In case of the tested device 36 sensors were used, but generally it depends on a tested device. The Raspberry Pi controlled the measurement process via an SPI serial interface. The results were collected from the oscilloscope via a UART/RS232 serial interface. The relation between frequency and temperature (Fig. 4) as well as 2D visualizations (Fig. 5) were made using Gnuplot and Scilab. The results should visualize the temperature distribution inside the device, but first right calibration of sensors should be made. The location of elements inside the FPGA sensor is of great significance, so in the case of an array of sensors, each ring oscillator should be analyzed and calibrated independently.%W artykule przedstawiono system pomiarowy, w którym nadrzędną rolę sprawuje mały, cieszący się coraz większą popularnością, mikrokomputer edukacyjny Raspberry Pi. System zaprojektowany został do wizualizacji rozkładu temperatury wewnątrz struktury układu reprogramowalnego FPGA, na podstawie dokonanych pomiarów częstotliwości oscylatorów pierścieniowych zaimplementowanych wewnątrz układu. Sterowanie procesem pomiarowym, akwizycja danych i prezentacja wyników nadzorowana jest przez mikrokomputer Raspberry Pi.