| With the rapid development of computer technology and digital technology, signalacquisition and signal processing systems are widely used in scientific research, industrialcontrol, aerospace and other fields. However, in reality, many of the external signals areanalog signals, they should be changed into digital signals by sampling, quantization andcoding, so that the computer can process them, and then do the subsequent processing andanalysis. Now the real-time digital signal processing becomes increasingly demanding, whichalso requires high-speed on extracting information from the data acquisition system and putsforward higher requirements.The paper designed a data acquisition card including hardware and driver underVxworks. The card is divided into two parts, named PMC card and AXM card,the PMC cardis a generic AXM carrier board, user can design their own AXM card for need, and thendesign flexibly in Spartan-6FPGA which is on the PMC to achieve different levels of signalacquisition and upload. The AXM card includes four AD signals and two DA signals, theanalog signals should be prepared firstly and then converted by AD converter, the converteddata is uploaded via the FIFO mode and DMA mode.The DMA mode which combines theadvantages named ping-pong mechanism and PCI bridge chip DMA transfer mechanism canachieve high-speed data upload. The DA mode contains three types: singlet mode, continuousmode, and loop mode. The single mode can be used to output a single voltage value, thecontinuous mode can be used to output non-periodic signal, and the loop mode can be used tooutput the periodic signal. In the driver design, all the functions are packaged into theunderlying modules, so it provides an interface containing menu commands which can callthose underlying modules, resulting in convenient interactive. Finally it builds across-compiler environment under Vxworks debug, and uses the menu commands to verify allthe functions, and gives a mathematical verification of the collected data of AD and DAoutput waveform, indicating that the design meets the requirements and the system is stable. |
