A High-speed And High-precision Data Acquisition System Based DSP And FPGA

With the development of modern testing technology, the data acquisition system (DAS) has to work at higher sampling rate and precision to record and measure some weak, high frequency and complex signals. Aiming the market demand, a high speed and high precision DAS, which can reach 250 MSPS, 12 bits resolution and 1M words storage depth, is discussed in this paper. The DAS makes the best of the powerful control and digital signals processing function of DSP and the flexible CPLD/FPGA which can works under high frequency.The paper emphasize particularly on sampling rate, data storage, system control, data traffic control, and so on. The detailed explanation of these aspects is described.Time-Interleaved sampling technology with multiple Analog-to-Digital converters (ADC) is used to gain 250MSPS sampling rate and maintain 12 bits resolution. For a high precision ADC chip, it's hard to buy one and its sampling rate is usually low. This method resolves the problem.Data storing is very important in high speed DAS. The DAS store the data with different phase. For the speed of the sampling data flow is too high, the system divides it by phase, and then stores it to four SRAM. At last, the storage capacitance reaches 1 Mega words. This method resolves the matching problem of the SRAM's low access rate and the ADC's high sampling rate, and it achieves the purpose of large-scale and high speed data storage by using low-speed and cheap SRAM.Because the number of the chip which can control the high speed ADC is small, the designed DAS make best use of the merit of high-speed and great capacity of CPLD/FPGA to control the system. The control strategy of the ADC chip and memorizer is developed by VHDL.By making the DSP and USB together, the DAS transmits the sampling data to computer system very fast and convenient.The designed DAS has large-scale data storage capacitance, high speed data transmitting rate. Beside this, it can sampling under trigger mode and its sampling rate is adjustable. It can work as a sampling module independently or a subsystem of the computer system. The paper discussed the DAS's hardware and software design, and some primary control circuit is tested by emulator. It finally points out that the DSP+FPGA based high speed and high precision DAS is a good choice.