An oscilloscope is a widely used electronic measuring instrument. With the rapid development of electronic technology, various types of electrical signals are becoming more and more complex. In engineering applications, the real-time sampling rate and waveform capture rate of signals are also high. Digital oscilloscopes are essential for hardware development and test personnel in various positions. tool. Aiming at the needs of current flexible industrial measurement systems, this paper presents the scheme of DSP+CPLD, which realizes the design of a high-precision, high-integration portable digital storage oscilloscope. The system uses digital integrated circuits as much as possible, and the structure is simple and the measurement results are obtained. High reliability, friendly human-machine interface, high sampling rate, high resolution and low error.
1 system design
The digital oscilloscope is mainly composed of two parts: measurement control and display output. The input signal is processed at the front end of the measuring circuit and processed into an equivalent signal that can be processed by each secondary unit via the signal conversion circuit. The comparison circuit processes the output of the square wave and the equivalent operational amplification output signal with a peak-to-peak value of 2.5 V. The square wave signal acts as a counting pulse, triggering the programmable logic device CPLD to measure the frequency value. At the same time, the signal outputted by the operational amplifier is input to the sample-and-hold, and the main controller DSP issues a latch signal to its associated pin to implement the function switching of the sampling and latching output of the signal to be tested.
When the control terminal is set to "1", it is a latched output. At this time, the output signal can be used for data acquisition by the A/D converter device; when "0" is set, the signal acquisition is realized. The data collected by the A/D is sent to the DSP, and then the DSP first stores the external data in the external memory, and then analyzes. Finally, the processed data is sent to the liquid crystal display through the RS 422 standard interface in the form of a data packet. Output. The system block diagram is shown in Figure 1.
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