Virtual instruments have developed rapidly in recent years. Virtual instruments utilize powerful computing and data processing capabilities of computers, save hardware overhead, and can take advantage of computer programming technology to achieve more complex functions. Based on this background, Cypress uses Cypress. Semiconductor's highly integrated, short-lived PSoC3 chip develops a virtual oscilloscope with low hardware overhead and powerful features. The oscilloscope is implemented based on the CY8C3866AXI chip. The measured analog signal is converted into a digital signal by the internal ADC of the chip. The signal is sent to the PC by the PSoC3 main control chip through the serial port (UART). The PC uses Visual Basic 6.0 to develop a visualization software to monitor The signal sent by the serial port and the digital signal is restored to the waveform of the analog signal. The software also provides a control panel to control the display and parameter setting of the oscilloscope.
0 PrefaceThe oscilloscope is one of the most basic instruments in electronic design. It can be used to observe the waveforms of digital and analog circuits, and can measure a series of parameters such as signal quality, voltage and frequency. However, this equipment is generally only available in the school laboratory and research and development department. The device is relatively expensive and is not generally owned by individual users. On the network, a sound card type oscilloscope is also developed using the system API. The oscilloscope can realize basic functions, but a notebook may be scrapped because it burns out the sound card of the computer or even the computer motherboard due to inadvertent use. And the sound card uses a limited data rate. This solution has inherent disadvantages. If another solution can be used, and the speed, cost, and burnout of the computer are not solved, the product must have a place in the market. After learning PSOC3, this is found. A perfect solution, Cypress Semiconductor's PSOC 3 chip includes a USB interface, MCU master, and high resolution ADC. This provides design convenience for a higher performance, low price, small size virtual oscilloscope.
This design utilizes PSOC's integrated internal unit module to implement hardware circuit functions through programming. The PSCOC chip communicates with the PC through some communication method, and the computer restores the digital signal to an analog waveform by parsing the data sent by the PSOC. And provide parameters such as waveform, voltage, and period.
1 overall designIn view of the volume and cost constraints of virtual oscilloscope products, the construction system of this paper has comprehensively considered the above factors. The core of the virtual oscilloscope is to realize the virtual oscilloscope with small size and low cost and multi-function by taking advantage of the high integration degree of PSOC3.
Figure 1 shows the overall block diagram of the virtual oscilloscope built by PSOC, which can be divided into three parts: (1) ADC sampling: PSOC3 comes with 8-bit ADC. (2) Serial communication: realize communication between PSOC and host computer (3) VB-based oscilloscope display software: use computer high-resolution waveform display and parameter setting, measurement, etc.
In this design, the CY8C3866AXI programmable device is used to collect and convert analog signals into digital signals. The digital signals are transmitted to the PC through USB. The PC analyzes the data stream sent by the PSOC and restores them to analog waveform signals.
figure 1
Comparison of several design options:
Table 1
Based on the comparison of the schemes of Table 1, our scheme 3 is a preferred design. Option 4 is an alternative and Option 1 is an experimental one.
Compared with the schemes 1, 2 and 3, the PSOC3 ADC configuration is more flexible, lighter and more convenient, and the hardware design is more concise. High integration greatly reduces development costs. PSOC3 facilitates the modification of software programs for functional extension. Users don't have to constantly buy new instruments, and they are small and effective.
Solution 3 uses USB 2.0 high-speed data transmission and is integrated with a high chip. You can design a virtual oscilloscope product that is better than the smaller one. But it is not conducive to long-distance industrial testing.
Go to scenario 4. In order to achieve low-frequency small-signal measurement in the field of industrial detection and control, Scheme 4 is more practical, and with the high integration of PSOC3, many analog conditioning circuits are saved. It also reduces the size of the device and enhances the reliability of the system. Therefore, this project adopts Option 4.
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