Basic competencies and knowledge that communication equipment hardware engineers should have

What is the level of technical requirements for hardware engineers?

Of course, from the childhood education we know that knowledge to understand thoroughly, the deeper the better, for any one point of knowledge, through the basic formula, using mathematical tools deduced to the last to verify the advanced laws and formulas. I think for this point, the college Entrance Examination physics is reached the pole, high school physics knowledge is not difficult, but we for the purpose of selection, the physics of various laws together, combined with some brain teasers, complex operations, resulting in college entrance examination physics is the most difficult subject.

If we take the spirit of the physical problems of the college entrance examination to solve the hardware problem, of course, the spirit is commendable, the work is worth encouraging the spirit of learning and exploration, but for the development of the project is not much benefit, after all, the work of hardware engineers is engineering development, within the specified time and budget to complete the hardware project, Instead of what formulas and calculations you derive from yourself at this time, it is the work of the scientists, that is the work of the researcher.

An important feature of engineering development is "stepping on the footprints of predecessors", is through the past dozens of hundred years of engineering practice, for various situations have a lot of experience data and experience, for example, for PCB layout, basically each company has its own design Guidelines/check List, this is the company in the past many projects summed up, each can be said to pay the price of "blood", which is for board-level design, for the core chip and device, it is even more so, chip or device company A few dozens a few years out of a chip and device, Or you can thoroughly understand it through hundreds of pages of datasheet.

In most cases, it is sufficient to know the main interfaces, parameters, functions and performance, especially the design guidelines or application notes provided by the chip/device company, which is typically a chip/device engineer's heartfelt words, experience, In general, engineers who don't have a decade or 20 years of work experience can not write these things.

Although it seems simple, it looks like nonsense, but careful analysis, combined with the circuit theorem and electromagnetic law, a little analysis, you will find simply Abas. Just graduated from the good students (generally study well, like to eat difficult problems, learning ability, thirst for knowledge strong) first-dry hardware design, will find involved in the knowledge points and technical points too much, if this knowledge point want to understand thoroughly, that knowledge point also to understand thoroughly, will find 24 hours a day is not enough, but sorry, Company please come over not to let you learn, is to do hardware design, after one months to see the schematic, you still holding the ORCAD manual a command to learn ORCAD use skills, research why to have a serial resistor, study the capacitance is to take 0.1uF or 0.01uF ....

Curiosity is a good thing, but that is in the spare time, the project, humbly to learn from the predecessors, as far as possible to use a variety of design guidelines, as soon as possible to complete the work, record their own knowledge shortcomings, in the leisure hours study hard, understand thoroughly, through design verification/testing, deepen knowledge of the point of understanding, This is the right way to work.

I just graduated from the joy of the discovery of transmission line theory is too important, and then spent one months to the transmission line theory efforts, and deduced a large number of formulas to verify, in fact, summed up is a few words, impedance matching, if the receiving end impedance is greater than the transmitting end, the signal will be how, if less, if the signal will do; What will happen, if the short-circuit, what will be, these basic every signal integrity of the book will be introduced, there will not be a very complex mathematical formula derivation, know on the line, and then how to balance the impedance of the transmitter end, serial resistance, PCB impedance, matching impedance and so on, are simple mathematical formula.

So, for those who are particularly strong in curiosity (such as me), sometimes must learn to "scratch", make full use of predecessors experience, to avoid falling into the technical misunderstanding, such as the formula is not used, you have to use the double integral deduction. The main feature of hardware development is "broad", what things to know, a good hardware engineer will have to understand a little, of course, some aspects can be deeper into the principle of the level of the better.

Like blog title said: about the hardware design of various technologies/standards/chips/devices are to know, when needed, can be handy, functional performance, parameter characteristics, advantages and disadvantages.

What are the basic knowledge and capabilities of that communication device?

1, the ability to learn quickly:

On the one hand, communication technology, standards, chip update too fast, fast to you at all too late to understand it, only through specific projects, needs to understand; On the other hand, the hardware products that need to be done are also changing quickly, customers need T1, E1, PDH, Sdh,ethernet, VoIP , Switch, Router, no one knows everything, need to be able to combine the needs of customers, the choice of chip solutions for detailed understanding, especially for interface protocols and electrical characteristics.

2. Understanding of communication protocols and standards:

Communication equipment, as the name implies, is used to implement a variety of communication protocols (such as T1, E1, V.35,PDH, Sdh/sonet, ATM, USB, VoIP, WiFi, Ethernet, tcp/ip,rs232 and so on commonly used protocols) to achieve communication equipment, various circuits, PCB board, power supply is for the communication protocol services.

Communication protocols are generally implemented by the chip, either the mature ASIC or the FPGA/CPLD, the chip engineer or the FPGA engineer is closer to the communication protocol than the hardware engineer, they need to understand the communication protocol thoroughly, Implement a variety of logic state machines and meet the requirements of the Protocol electrical parameters standards. According to the OSI seven-tier model, hardware engineers especially need to focus on a layer of physical layer and two layer Data Link layer protocol standards to Ethernet distance, the physical layer is completed by the Phy/transceiver chip, the data link layer is completed by the Mac/switch chip, For hardware engineers engaged in Ethernet related development, the PHY and switch chips need to be understood thoroughly, from coding, electrical parameters, eye standard, template, signal frequency to frame format, forwarding processing logic, VLAN and so on.

For the traditional pdh/sdh/sonet equipment is more so, pdh/sdh/sonet is a more hardware device, that is, the main protocol is implemented through the ASIC, the function of the software is mainly management, configuration, monitoring, alarm, performance, for hardware engineers, Must be familiar with the relevant protocol and interface standards used, especially for electrical specifications, eye Diagram template, so that in the design verification can be confident.

3, the ability to write documents:

As software design, good software design needs good design documents, clear requirements, what functions to achieve, to achieve what acceptance standards, with the increase in chip integration, interface rate, increase the complexity of the single board, hardware design is more and more complex and corresponding to thermal stability, reliability, electromagnetic compatibility, environmental protection requirements, No, it's not through the millet. Guerrilla warfare can be solved, every hardware project is a war, all need good planning, good analysis, which requires good documentation.

For hardware engineers, there are two of the most important documents: one is the hardware design specification (Hds:hardware Designer specification) and the Hardware test report (commonly called evt:engineering validation& test Report or Dvt:design Validation & Test report), the requirements for HDS are informative, clear, main chip selection/hardware initialization, CPU selection and initialization, interface chip selection/initialization/management, Connection diagram between each chip (block Diagram), DRAM type/size/speed, flash type/size/speed, chip selection, interrupt, gpio definition, reset logic and topology diagram, clock/crystal selection/Topology, RTC usage, memory mapping MAP) relationship, I²c Device selection/topology, interface device/line order definition, LED size/color/drive, heatsink, fan, JTAG, power topology/timing/circuit, etc.

For DVT, the requirements are simple and complex: what interface on the board, chip, main device, circuit, it is necessary to test what, especially in the case of the Board normal operation of the power/voltage/ripple/timing, business interface of the eye Diagram/template, the internal data bus signal integrity and timing (such as Mii, RGMII, XAUI, PCIE,PCM Bus, Telecom bus, SERDES, UART, etc.), CPU subsystem (such as clock, reset, Sdram/ddr,flash interface).

A good hardware engineer, whether it is a document or a report is a clear, what the hardware system needs to use the program and circuit, and finally verify the results of the test. Full content, not missing all kinds of interface/circuit; simple name, no nonsense; illustrated, when needed a time series diagram, an oscilloscope capture is a good illustration of the problem.

4, the use of instrument/software capabilities:

Instruments include soldering iron, multimeter, oscilloscope, logic Analyzer, error meter, transmission Analyzer, Ethernet tester Smartbits/ixia, calorimeter, attenuator, optical power meter, RF signal strength meter and so on; software includes office (Outlook,word, Excel, PowerPoint, Project, Visio), PDF, common schematic software pads or ORCAD, common PCB software pads or Allegro,allegro Viewer, circuit emulation software PSpice, Signal simulation software hyperlynx and so on.

Whether the instrument or software, in the political economy is said to be a production tool, is to promote productivity improvement, as a hardware engineer, These instruments and software are the hands of the wood. Silo Cannon, hardware engineers a large part of the ability of the embodiment of the instrument and software, especially for the use of schematic software and oscilloscope, is very important, the use of schematic software is the implementation of hardware design, through a device placement, a net connection, constitutes a very complex hardware logos Software, is the core of the entire hardware design work, any one schematic errors and mistakes caused by the loss are huge, really "walking on thin Ice, trembling."

In addition, the use of schematic software is also reflected in the schematic diagram of the beautiful, good design, simple and clear, clear annotation, regardless of who, along the way can quickly make clear design intentions, need special attention, bad design, east a device, a device in the West, no logic, named weird, difficult to understand, It is very troublesome to maintain in the future. Oscilloscope in all the test instruments, for the hardware engineer is the most important, regardless of the schematic or PCB is the design work, but any design needs careful verification test, especially in the signal aspect, need a lot of oscilloscope work, Do not correctly use the oscilloscope is not the correct verification, grounding is not connected, test point selection, trigger choice, delay choice, amplitude, time selection, all determine the test results. If the wrong use of the oscilloscope is bound to bring the wrong test results, in this case, it is possible that the wrong design was mistaken for the right, causing a huge hidden danger; it was wrong to think that the right design was mistaken, resulting in a lot of wasted time and energy.

5, the ability of circuit design:

As the chip integration increases, the hardware design seems to be simpler. The first is the logical connection, followed by the signal integrity needs of the serial resistor selection and parallel capacitor selection, power filter, decoupling. But for a good hardware engineer, a simple logical connection (the chip's output of the same bus to another chip input, and so on), just the most basic hardware design skills, the circuit is a chip function, communication protocols and various software carrier, no deep understanding of the circuit, there is no deep understanding of the hardware design, In particular, the electrical performance parameters on the back column of the chip or the understanding of various parameters of discrete devices, random random connection, May be on the 3.3V bus can work, but now the operating voltage has been reduced to 1 V, what concept, signal line noise is already large enough to make sampling error, with the increase of signal rate and the reduction of operating voltage, digital signal has been more and more simulated, it is necessary for the PCB impedance, tolerance, inductance, discrete devices (resistors, capacitance , inductors, diodes, transistors, MOSFETs, transformers, etc.), ASIC interface electrical parameters in-depth understanding, which requires the circuit principle, analog circuit even electromagnetic field theory in-depth study, the circuit can be said to be a subset of the theory of electromagnetic field, there is no understanding of the theory of electromagnetic field, there is no capacitance, inductance, crosstalk, Understanding of electromagnetic radiation.

Especially for the power circuit design, now the chip voltage diversification, voltage is getting lower and larger current, operators for communication equipment, the stringent requirements of power dissipation, the challenge of power supply design more and more large. It can be said that for a hardware design, 40% of the work is in the power supply circuit schematic/PCB design and post-test verification, power supply circuit design is a hardware engineer circuit capability of the centralized embodiment, a variety of passive devices, semiconductor devices, protection devices, DC/DC conversion Typical topology, there are many parameters, The formula needs to be considered, calculated to.

6, the ability of communication and global control:

Hardware Engineer in a hardware project, generally in the role of team leader, to the full responsibility of this hardware project, need to coordinate the PCB engineer, structural engineers, signal integrity engineers, EMC engineers and other resources, and with product managers, project managers, software engineers, production engineers, Sourcing engineers work closely together to ensure that every step of the project is well-understood, that the release time of each sub-task, and the estimation of possible technical difficulties and risks, are controlled.

For the outside, the hardware engineer also with the chip distributor, Fae to deal with the relationship, to obtain greater technical support and help; with EMC Labs, external labs to get more flexible testing time and more corrective advice.

Basic competencies and knowledge that communication equipment hardware engineers should have