"For hardware designers, they are bound to be exposed to various test instruments, such as multimeter, oscilloscope, signal generator and so on. Oscilloscope can be said to be the most commonly used tool for debugging or measurement. The oscilloscope converts the measured signal into voltage signal and records and displays it in a time domain, so that engineers can observe the change of signal in a period of time, which can greatly improve the efficiency of engineers.
Oscilloscope generally includes acquisition, analysis, display and storage. Analog oscilloscopes first appeared. In the 1990s, digital oscilloscopes were gradually widely used with the improvement of performance. Although analog oscilloscopes have some advantages, such as high real-time sampling rate, the whole trend is gradually replaced by digital oscilloscopes. For example, Tektronix has long stopped producing analog oscilloscopes.
The important indicators of digital oscilloscope generally include bandwidth, sampling rate and storage depth. With the progress of technology, the sampling rate of digital oscilloscope has been continuously improved. The real-time sampling rate of the world's highest bandwidth oscilloscope launched by Agilent has reached 160gsa / s, which can be said to have completely surpassed the analog oscilloscope. On the one hand, the sampling rate and other performance indicators of digital oscilloscope are improving continuously, while on the other hand, digital oscilloscope is developing towards small and portable.
The volume of analog oscilloscope is limited by CRT display tube and can not be too small. With the progress of semiconductor technology and the development of integrated circuit, the volume of digital oscilloscope becomes smaller, but the performance continues to improve. For some occasions with low requirements, there are even handheld portable oscilloscopes. It is precisely because of the emergence of digital oscilloscope that the functions of data acquisition and processing and analysis and display can be separated. Therefore, a so-called virtual oscilloscope also appears. That is, after the signal data is collected and stored, it is transmitted to PC through USB, and the processing capacity of PC is used for analysis and display, so that the oscilloscope can be made smaller and portable. Aiban once disassembled a ds-1302 virtual oscilloscope produced by acute in Taiwan.
Virtual oscilloscope has incomparable advantages in portability and can fully meet the general signal measurement requirements. However, it needs to be used with a computer to transmit data through USB. In fact, it is to replace the host of the oscilloscope with a computer, and all measurement operations are carried out through the software on the computer.
With the popularity of mobile Internet, the processing capacity of mobile phones and tablets has been comparable to that of PCs, and various intelligent hardware emerge in endlessly. How traditional oscilloscopes, especially virtual oscilloscopes, adapt to the development of the new era is also a very interesting topic. The weishirui wavexpert intelligent measuring instrument just evaluated by aiban.com is a very meaningful attempt. Portable, wireless and cloud, wavexpert has all the elements of the current popular intelligent hardware. What is its internal structure? AI ban net engineers will come slowly.
Wavexpert intelligent measuring instrument
If wavexpert is used as an oscilloscope, the main parameters are as follows:
Sampling rate: 100MHz
Accuracy: 12bit
Channel: dual channel
Bandwidth: 10MHz (sine)
Input impedance: 1m
DC coupling mode
Maximum input voltage: - 5V ~ + 5V (X10 probe)
Maximum input voltage: - 250Mv ~ + 250Mv (x1 probe)
Internal trigger: edge / level
Screen resolution: 1000 points
Sampling depth: up to 5242880 points
Data processing capacity: about 1Mbps
Waveform refresh rate: 30fps
Dead time: about 30ms
For more detailed information about weishirui wavexpert intelligent measuring instrument, please refer to the evaluation article of aiban.com. Next, we will disassemble wavexpert to learn more about its design.
Wavexpert disassembly
In the evaluation, it has been learned that waveexpert has a large heating capacity, and the design of the corresponding aluminum alloy shell is very kind and ideal for heat dissipation. Similarly, the engineers of Aiban network are very simple and convenient when disassembling wavexpert, which can be done by unscrewing four screws.
Wavexpert family photo
It is worth mentioning that the structural design of the wavexpert aluminum alloy shell is a bit like an intelligent router. The main board and the shell are fixed through a drawer structure. However, compared with the intelligent router, the wavexpert shell is more free. Through the ingenious structural design, the upper and lower box covers can be stuck or separated from each other.
Let's look at the motherboard. The motherboard design of wavexpert still gives people some surprises. There is another mystery. There is also a core board on the back of the motherboard, which is connected through DIMM gold finger interface. This design is undoubtedly more conducive to providing engineers with a DIY and customizable platform. As shown in the figure below
Remove the core board. There are almost no circuits on the back of the motherboard, so we still focus on the front of the wavexpert motherboard and the core board.
Wavexpert motherboard
Ti ads4225 (ads4225 Data Book) ADC converter
Due to the engineering prototype, we can find many changes on the motherboard after careful observation, such as the jumper at the input end of ADC and the jumper at the output end of DAC. In addition, we can see that the solder of the reset indicator on the motherboard has fallen off and belongs to the disconnected state. However, these small problems do not prevent us from understanding the principle of wavexpert. We still focus on the AD converter and DA converter, the two core IC devices on the board.
Wavexpert motherboard front
Wavexpert motherboard core resources:
ADC conversion: Ti ads4225 (ads4225 Data Book) ADC converter
DAC conversion: ADI ad9788 (ad9788 Data Book) DAC converter
Peripheral interfaces: power supply / usb-to-uart microusb interface, microSD card holder, Gigabit Ethernet port, USB host interface, PMOD interface, JTAG interface, etc
On board IC devices: silabs cp2301 usb-to-uart, ATMEL at88sc encryption chip, linear / Ti buck converter
When wavexpert is used as an oscilloscope, the main work of sampling is completed by ad chip. On the main board of wavexpert, the design of AD sampling function is realized through Ti ads4225. This is a 12 bit dual channel ADC converter, 1.8V single voltage power supply, up to 125msps sampling rate, which is packaged in qfn-64 (9mm * 9mm). Ads4225 also has a very low power consumption of 277mw @ 125msps.
SFDR, the full English name is spurious free dynamic range. It means spurious free dynamic range, which is used for the index of a / D converter and D / a converter (ADC and DAC).
In addition, ads4225 has high dynamic performance. It can improve SFDR by adjusting the gain and cancel the offset of ADC through the internal DC offset correction loop. The brief working principle is shown in the figure below. In addition, the detailed indicators of ads4225 can be found in the data manual.
Brief working principle of ads4225
ADI ad9788 DAC converter
Another important IC device on wavexpert board is the DAC converter ads9788 that realizes the function of signal generator. Its functional block diagram is shown in the figure below
Ads9788 DAC converter features:
Adjustable analog output: 8.7 Ma to 31.7 Ma, RL = 25 Ω to 50 Ω
Low power precision complex NCO allows the carrier to be set anywhere within the DAC bandwidth, while the increased power consumption is less than < 300 MW
The auxiliary DAC supports I and Q gain matching and offset control, including programmable I and Q phase compensation
Internal digital up conversion function, multi chip synchronous interface
High performance, low noise phase locked loop (PLL) clock multiplier
Digital inverse sinc filter
100 pin, bare pad TQFP package
Ads9788 is a 16 bit high dynamic DAC converter using 0.18 μ M CMOS process, supporting 1.8V and 3.3V power supply. Ads9788 can realize the sampling rate of 800MSPS. In the application of practical products, DAC output is optimized and can interface seamlessly with analog quadrature modulator, such as adl537x series of ADI company; Serial peripheral interface SPI allows programming and readback of many internal parameters; The full-scale output current can be programmed in the range of 10 Ma to 30 ma.
In addition, ads9788 also has very prominent features, such as:
Using the characteristics of low noise and intermodulation distortion (IMD), broadband signals from baseband to high and medium frequency can be synthesized with high quality
Proprietary DAC output switching technology for enhanced dynamic performance
CMOS data input interface, with adjustable establishment and holding function
Low power complex 32-bit controlled oscillator (NCO)
Ads9788 is very suitable for wireless infrastructure, digital high and low if synthesis, broadband communication and other application fields.
Wavexpert core board
If the motherboard is equipped with the main interface circuit design to interact with the outside world, the core board is the data processing center. The wavexpert core board looks very small, similar to the notebook memory module we usually see.
Wavexpert core board
Main devices on the core board:
XILINX ZYNQ XC7Z010-CLG400 Soc，17mm*17mm
Marvell Gigabit Ethernet transceiver 88e1116r (88e1116r Data Book)
Microchip USB interface integrated circuit usb3320c (usb3320c data manual), NAND flash, SDRAM
The main components of the core board are Xilinx zynq xc7z010-clg400, which is an entry-level product in Xilinx zynq xc7000 series:
Zynq xc7000 series
Even so, the structure of zynq xc7z010-clg400 is still very large and complex. We can simply understand it as a programmable SOC with two arm cortex-a9 cores integrated inside, and the main frequency is 1GHz.
In addition to the main SOC of Xilinx zynq xc7000 series, the core board is also equipped with Marvell 88e1116r transceiver to realize Gigabit Ethernet function and microchip usb3320c to realize USB interface function. In addition, the core board is also equipped with NAND flash, daram and other devices, which will not be introduced one by one here.
Through the disassembly of waveexpert, we can easily draw its brief principle block diagram, as shown in the figure below
Brief hardware principle block diagram of waveexpert
Of course, the wavexpert is more than just an oscilloscope. Its innovative design concept makes the product a multifunctional electronic measuring instrument. For example, by burning different startup image files through microSD and configuring FPGA, different functions can be realized, such as signal generator, protocol analyzer, logic analyzer, etc., which also reserves a certain space for engineers to realize secondary development.
Finally, we will compare wavexpert and acute previously evaluated by Aiban Compare ds-1302 virtual oscilloscope:
Weishirui wavexpert vs Huangjing acute DS-1302
Summary
The engineering prototype of wavexpert, an intelligent measuring instrument of weishirui, was disassembled. Although wavexpert is not a very mature product, it is found that it has great potential through disassembly. Different from the current virtual oscilloscope using USB transmission, wavexpert can be connected to PC, mobile phone and tablet through wired or wireless network. The advantages of wavexpert are:
The sampling rate is up to 100ms / s, and the latest zync SOC FPGA is used internally.
Scalable secondary development capability and reconfigurable FPGA make wavexpert not only be used as an oscilloscope, but also be configured as signal generator, logic analyzer and protocol analysis, so as to realize the integration of multiple instruments and truly be a laboratory in hand.
The function of wireless connection makes it more convenient for mobile devices such as mobile phones and tablets to test, and the storage, sharing and analysis of test waveforms are more convenient.
Wavexpert can be said to be a transformative product. Of course, there are still many deficiencies at this stage. For example, only DC coupling, single trigger mode, small amplitude and so on. Especially at present, the software is not perfect. We just try the software of oscilloscope and signal generator. Although the basic functions are realized, the data processing and calculation are still very simple. It can be said that there is still great potential.
Cheap, powerful and integrated equipment with a variety of measuring instruments is the dream of every geek or electronics enthusiast. Wavexpert is especially suitable for teaching or electronic enthusiasts. It can be fully competent for some basic measurement tasks, such as Arduino, raspberry pie commonly used by geeks or signal measurement when using radio. Of course, there is still much room for improvement in the software and hardware of wavexpert. For its users, it is a good direction to completely open source wavexpert, which may make it a truly revolutionary measuring instrument.
reference material
"Crazy, measuring instruments also start to play smart" -- simple experience of weishirui wavexpert
Disassembly of acute ds-1302 virtual oscilloscope
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