Here is just a summary of IO control related and this kind of bus, etc. ~ Continue to update the fourth part whaosoft aiot http://143ai.com
Here, the oscilloscope is also written~~ Anyway, it is also related
1. How to choose an oscilloscope
Oscilloscope is one of the necessary tools for electronic engineers, and it is often used in circuit design, PCB manufacturing, electronic equipment maintenance and other scenarios. An oscilloscope is so important, what should we pay attention to when purchasing an oscilloscope? Let's take a look at the 10 factors to consider when choosing an oscilloscope.
1. Bandwidth
The bandwidth determines the ability of the oscilloscope to measure analog signals, which determines the maximum frequency that the instrument can accurately measure. Bandwidth is also a key determinant of price.
Determine your needs before choosing an oscilloscope. For example, a 100 MHz oscilloscope is typically guaranteed to have less than 30% attenuation at 100 MHz. To ensure better than 2% amplitude accuracy, the input should be below 20MHz.
Use the "rule of five" when choosing bandwidth. The oscilloscope bandwidth is greater than or equal to five times the maximum frequency you want, if the bandwidth is too low, your oscilloscope will not be able to resolve high frequency changes.
A basic oscilloscope typically has a range of 50 MHz to 200 MHz. If you need more bandwidth, you can use a higher performance oscilloscope to cover beyond 350 MHz and reach tens of GHz.
2. Sampling rate
Sample rate (samples per second) is the rate at which the oscilloscope samples the signal, similar to the frame rate of a video camera; this determines how much waveform detail the oscilloscope can capture.
Again, we recommend using the "rule of five": use at least 5 times the sampling rate of your circuit's highest frequency components.
Most basic oscilloscopes have a (maximum) sample rate of 1 to 2 GS/s. Remember that basic oscilloscopes have bandwidths up to 200MHz, so scope designers typically design scopes with 5 to 10 times oversampling at maximum bandwidth.
The faster the sampling rate, the less information will be lost and the more effectively the oscilloscope will be able to represent the signal under test; however, it will also fill up the memory sooner, which in turn limits the amount of time that data can be acquired.
Most entry-level oscilloscopes have a maximum sample rate of 1 to 2 GS/s, while mid-range oscilloscopes can have a maximum sample rate of 5 to 10 GS/s.
3. Sufficient input channels and correct channels
Oscilloscopes use analog channels to store and display signals. In general, the more channels the better, although adding channels will increase the price.
Whether you want to choose 2 or 4 analog channels will depend on your application. For example, you can use two channels to compare the input and output of components. Four analog channels allow you to compare more signals and provide greater flexibility to combine channels mathematically (for example, multiply for power, or subtract for differential signals).
But beware: the number of channels you turn on may reduce the sample rate.
4. Compatible probes
Good metrology starts with the probe tip. Oscilloscopes and probes work together as a system, so be sure to consider probes when choosing an oscilloscope.
During the measurement, the probe actually becomes part of the circuit, introducing resistive, capacitive and inductive loads (changing measurements). To minimize the effect, it is best to use the special probes that come with the oscilloscope. A wide range of compatible probes will allow you to use your oscilloscope in more applications.
In addition, it is also important to choose a passive probe with sufficient bandwidth. The bandwidth of the probe should match the bandwidth of the oscilloscope.
Classification of probes
Passive probes:
Passive probes have a 10x attenuation, exhibit the controlled impedance and capacitance of the circuit, are suitable for most ground-referenced measurements, and come with most oscilloscopes. You will need one passive probe for each input channel.
High Voltage Differential Probes:
Differential probes allow safe and accurate floating and differential measurements with ground-referenced oscilloscopes. Every lab should have at least one!
Logic Probe:
Logic probes provide digital signals to the front end of a mixed-signal oscilloscope and include "floating leads" and accessories designed to connect to tiny test points on a circuit board.
Current probe:
If you add a current probe, you can let the oscilloscope measure the current, of course, you can also let the oscilloscope calculate and display the instantaneous power.
5. Trigger
Triggering provides a stable display, allowing you to adjust zeroing on specific portions of complex waveforms.
All oscilloscopes offer edge triggering, and most offer pulse width triggering. And the wider the range of trigger options available to an oscilloscope, the more flexible the oscilloscope (and the faster you'll find the source of your problems!)
6. Record length
The record length is the number of points in a complete waveform record. In general, oscilloscopes can only store a finite number of samples, so the longer the record length, the better.
Acquisition time = record length / sampling rate
So, with a record length of 1M points and a sampling rate of 250 MS/s, the oscilloscope will capture 4 ms.
A good basic oscilloscope typically stores over 2,000 points, which is more than enough for a stable sine wave signal (maybe 500 points). However, to find out the cause of timing anomalies in complex digital data streams, the record length of more than 1M points should be considered.
Oscilloscopes with record lengths in the millions of points can display many pictures of signal activity, an essential feature for studying complex waveforms.
7. Automatic measurement and analysis
Automated waveform measurements make it easier to get accurate numerical readings.
Most oscilloscopes provide front-panel buttons and/or on-screen menus for accurate automated measurements, including amplitude, period, and rise/fall time. Many digital oscilloscopes also offer average and RMS calculations, duty cycle and other mathematical operations.
For example, the channel calculation function allows you to perform operations such as addition, subtraction and multiplication on waveforms. Use the waveform multiplication function to multiply voltage and current to obtain power values; use the subtraction function to roughly estimate differential measurements. The Fast Fourier Transform (FFT) function will allow you to view the frequency spectrum of the captured waveform.
8. Easy to operate
It is important that an oscilloscope be easy to operate, even for occasional use. Ease of use criteria include:
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Frequently used adjustment functions should have their own dedicated knobs.
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AUTOSET and/or DEFAULT buttons will be available for instant setting.
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Oscilloscopes respond and react quickly to changing events.
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The oscilloscope should support your language and include a menu system, built-in instructions, manuals and appropriate front panel descriptions.
9. Connectivity
Connecting the oscilloscope directly to a computer or transferring data via portable media allows you to perform advanced analysis and simplify documenting and sharing results.
Many oscilloscopes, for example, can generate JPG, BMP, or PNG files to easily incorporate material. Many oscilloscopes come with software, or make it available for download, to help capture screen shots, collect waveform data, or store instrument settings. Some oscilloscopes also provide a VGA output, allowing you to connect an external monitor for easy viewing.
When choosing an oscilloscope, you can see what features you need, and off-the-shelf drivers can save you significant time and effort.
10. Serial bus decoding
Most system-level (computer-to-computer) communications are carried over serial data connections. Even on today's circuit boards, most chip-to-chip data travels over the serial bus.
Some oscilloscopes can decode serial buses and display other waveforms time-correlated to the data. Automatic decoding is much less time-consuming and less error-prone than manual decoding. In addition to decoding, some oscilloscopes offer the ability to trigger on and search for values in serial data. These features help speed up the troubleshooting process.