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As an electronic engineer, everyone should be unfamiliar with Digilent, maybe many people also see that the company's products are only come in and see, but still with doubts? What product is this reviewed OpenScope MZ?
OK, simply, Digilent OpenScope MZ is a multi-function tester, which has multiple functions such as oscilloscope, waveform generator, logic analyzer, power supply, data collection, but not only, it is still an open source hardware platform In addition to the functions of the above test measurements, it can also make engineers, electronic enthusiasts to develop, assess, DIY, etc., is it very attractive to open source platforms like the development platform on the market?
OpenScope MZ
Said so much, let's take a look at the product, there is a way to blow the sky, it is better to see it.
Digilent style minimal packaging, one internal OpenScope MZ, one of DuPont line, for signal measurement.
As far as I know, OpenScope MZ is in KickersTarter, and now there is also selling in the official website of Size Electronics, but the tax price will be nearly 750, and for domestic engineers, it may feel some little expensive. Some main features of Digilent OpenScope MZ:
2 12-bit oscilloscope channels, 2MHz bandwidth, maximum sampling rate is 6.25 ms / s
1 signal generator output, 1MHz bandwidth, update rate is 10 ms / s
10 User Programmable Pins, can be configured as a logic analyzer for user programmable GPIO or 10 channels
User programmable power supply provides up to 50mA current @ ± 4V
MicroSB interface power supply or external power supply
Onboard WiFi module, implement mobile phone interface operation
Provide a browser-based WaveForms Live multi-function instrument software that is available offline
Developer programming can be re-developed via Arduino IDE or Microchip Mplab X IDE
After reading these features, I believe that everyone has a certain understanding of this board, and the engineers who have exposed to virtual oscilloscopes will not be unfamiliar, but compared to the traditional oscilloscope for testing measurements, the parameters of OpenScope MZ are somewhat unattling, and More use environments may be the most valuable function as a logic analyzer. Specifically, look at the onboard resources.
(Click on the picture to enlarge)
The function distribution of the onboard is very clear, mainly to form an analog front end + ADC circuit that constitutes an oscilloscope function, a DAC circuit, + / - 4V power supply circuit, a logic analyzer function circuit, a WiFi communication module circuit, and a USB turn serial port. Circuit.
Further refine, first, look at the master.
OpenScope MZ is equipped with Microchip's PIC32MZ 32-bit microcontroller with 330 DMIPS and 3.28 Coremarks / MHz performance, and integrated large Flash (up to 2MB), large RAM (512KB) and various peripheral resources. . In addition, the PIC32MZ MCU also integrates a 10/100 Ethernet MAC, high-speed USB MAC / PHY (for the first time for PIC MCU) and dual CAN ports, of course, one of the most important points of MCU is integrated 12-bit ADC This is also an AD conversion circuit that makes up the function of the OpenScope MZ oscilloscope.
The main features of the microcontroller are as follows:
200MHz / 330DMIPS, MicroAptiv kernel
DSP enhanced kernel
Double-panel flash memory, realize on-site update support
12-bit, 28 MSPS, 48 channel modulus converter module
Memory management unit implements the optimum implementation of embedded operating systems
MicroMips mode can achieve up to 35% code compression
CAN, UART, I2C, PMP, EBI, SQI & analog comparator
SPI / I2S interface for audio processing and playback
High Speed USB 2.0 Equipment / Master / OTG
10 / 100Mbps Ethernet MAC with MII, RMII interface
As shown below is the ADC analog front-end circuit of the oscilloscope, OpenScope MZ implements two channel oscilloscopes per channel 12-bit resolution through the ADC inside the PIC32MZ MCU, each channel has a pair of analog inputs, one of the PWMs to process input offset voltages A DMA channel transmits measurement data in a second high priority.
Therefore, the main features of the oscilloscope are:
2 channel, 12-bit resolution per channel
6.25 ms / s per channel
2 MHz bandwidth @ -3 dB
Input impedance is 1MΩ
Input voltage range ± 20 V
Maximum buffer size 32640 samples per channel
DAC circuit, the current DAC everyone knows that the digital-to-analog conversion IC, but a small person is internally principled, only knowing that the digital signal will then output analog signal after this black box, in fact, the current DAC mainly has R2R architecture and resistive string architecture, If it is in closed-loop applications, there is a lower cost and poor linear resistance string DAC is sufficient; if it is in an open loop application, the R2R architecture is providing better linearity and higher precision. It looks more excellent. At this point, the DAC function on the development board has a R2R architecture plus an operational amplifier to form a circuit with a DAC function, and the voltage signal generated by the R2R network is converted into an output voltage.
The DAC circuit on the OpenScope MZ board forms a 10-bit function generator with single channel 10 ms / s. With the R2R resistance ladder with a 1% resistor, instead of DAC, due to the nature of the resistor, it may encounter a propagation delay for the steps of greater than 3 mV, which is one of the disadvantages.
DAC functionality composed of functional generator support:
Sine wave, triangular wave, sawtooth wave, square wave and DC output
10-bit resolution
1 Hz to 1 MHz frequency
3 V PK2PK output, ± 1.5 V offset
20 mA output current
25000 sample buffer size
OpenScope MZ has two DC outputs, driven by the PWM, including a single PWM line for DC offset. A gain circuit is added to the OpenScope MZ, providing the voltage range of -4 V to 4 V for each channel, and also provides a feedback circuit to allow calibration DC output.
DC output characteristics:
Two channels, ± 4 V
50 mA @ per channel
All interfaces of the OpenScope MZ are extracted by signal interface, including oscilloscopes, functional generators, DC output and other functions, with 10 user IO pins in the signal interface, between logic analyzers and digital input / output pins. Sharing, the DMA channel (functional generator function) shared with the highest priority AWG is used to transmit data received by PIC32MZ.
10 channel logic analyzer and universal IO multiplexing
3.3V CMOS logic
7 mA pull current and 12 mA perfusion current when used as GPIO
Logic analyzer's sampling rate is 10 ms / s
The largest buffer size of the logic analyzer is 32640 samples per channel.
The WiFi module on the OpenScope MZ is MRF24WG0MA of Microchip. Here, the WIFI module is used as an app to connect the mobile phone to implement the portable mobile function of the OpenScope MZ test measuring instrument.
The USB serial port circuit, OpenScope MZ handles signal data control between the host and the connected OpenScope MZ via the FTDI FT232RQ USB serial converter. Be
The user can interact with the OpenScope Mz in the menu mode or JSON mode, and the lowest priority pair of DMA channels are dedicated to UART, and if any other DMA channel stops UART DMA, all communication with the host will stop.
The following hops originally switched the USB interface of the USB to the serial port and the USB function interface of the onboard MCU, but because the board is not a patchboard MCU's USB function interface, it is useless.
MicroSD card, you can copy the upper computer software WAVEFORMSLIVE for the PC side to MicroSD to achieve offline data. This is very practical. After all, through the author multiple times, the networked data observation is not too friendly for domestic users. It may be the reason for the server abroad.
OpenScope MZ use
Users who have used similar virtual testers should be unfamiliar. The use of this instrument requires a software software, but OpenScope MZ is further, in the networked state, only need to access http://waveformslive.com/ can be implemented The function of the UI side. However, this is a relatively convenient for foreign users. For domestic users, it can quickly open this website to count me, so,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
Download Client Digilent Agent for Mac, Windows, Linux.
Take Windows as an example. After installation, you can see the icon of this software in the lower right corner, you can update the software or log in to the OpenScope MZ tester interface.
Connect the MicrousB of the OpenScope MZ to the PC side automatically install the USB serial port driver.
In the WaveFormslive interface, there are 3 configuration buttons, corresponding to WiFi networks, tester interfaces, and Agent configuration.
To use the tester interface, you must first configure the serial port in Agent.
Since the OpenScope MZ, which is about the author, the internal firmware is very old, and then updated the down firmware after configuring the serial port, but the firmware update is more mistake, the user experience is not too good.
The new firmware is updated, which typically requires calibration, calibration is the port of its own DC output to the oscilloscope.
Pay attention to the accuracy of the cable, where there is a place where you need to spit, the official is provided with a whole DuPont connection interface, resulting in could not be flexible to apply to the OpenScope calibration project, such as the OpenScope calibration project, really unused.
Basically prepare for work, you can use the tester's functionality through Simulate. The layout of the tester is also calculated that the mid-ruled medium, the display interface on the left, the right side is the function of the oscilloscope, signal generator, logic analyzer, voltage output.
Mobile phone control
Don't forget that OpenScope MZ is equipped with WiFi, so the author is more interested in how to implement the test measurement of data signals through the mobile terminal. Seriously, this configuration is really a bit unusual way, OpenScope MZ's onboard WiFi implements a STA function, requiring WiFi to connect to the same LAN in the mobile phone, so that the mobile app can directly with the board through the IP address Establish communication.
If the WiFi process is configured, there is not much, it is inconvenient. It may also be because of the opening and sources of project, many things are not perfect and intimate. Just take the accessories, only one interface seat with DuPont line may only be more convenient to test the pin-up interface of the development board itself, but the palette, reliable test for other project lines. A big problem, helpless, the author can only connect to the channel of the oscilloscope with a separate DuPont line through the channel of the signal generator, and realize the output, detection of the signal, and simply with the self-entertainment.
Sine wave
Triangular wave
Sawtooth wave
Square wave
Fourier transform.
Since there is no related accessories, such as the following similar to the BNC interface, the oscilloscope and other functions such as the OpenScope MZ board cannot be implemented.
It is not deny that the board itself works, the design, the layout is equal, but the practical words are poor, especially if there is no many peripherals, the light board is simply nothing to use, and the BNC interface is required. , A mini test clip that needs to collect signals. In addition, the price of 750RMB, believes in many domestic users are not optimistic, after all, some higher bandwidth, more channel virtual oscilloscopes are just about a thousand yuan.
From the case used by OpenScope MZ, you can summarize the following points:
Oscilloscope function: Function compared to other more comparisons, but because there is no BCN adapter, it is impossible to measure the performance of the oscilloscope, such as how much the real bandwidth can reach, and the product's standard 2MHz bandwidth can only smile.
Signal generator: only 1 channel, bandwidth 1MHz, output voltage 3Vpp
Logic analyzer: It is a bit stupid, and it is impossible to adjust the electricity.
Power supply output: 50mA @ + / - 4V output is basically no big, after opening the power output, the software can't turn off the output again.
Maximum bug: often does not respond
Small knot
For integration, OpenScope MZ does not loses a creative product, combining the measurement test instrument and microcontroller board, I want to do a clear stream in the open source, but a bunch of problems plus 750RMB's price is difficult to adapt to China. " The cost-effective "market, so that the author will lose interest and then experience, return to the title of this article," Flexible, open source, multi-function, electronic engineer's good assistant? "When the author truly experienced, he had to give this title. Take a question mark. "
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