A good hardware engineer is actually a project manager. You need to get the needs of your own design from the outside world, and then summarize and analyze it into a concrete hardware implementation. Also contact with a number of chip and solution providers to select the right solution. When the schematic is complete, you need to organize colleagues to coordinate review and inspection, and work with the CAD engineer to complete the PCB design. At the same time, you should prepare the BOM list, start purchasing and preparing materials, and contact the processing factory to complete the board placement. â€
1. Basic knowledge1) Basic design specifications
2) CPU basic knowledge, architecture, performance and selection guide
3) MOTOROLA's PowerPC series basic knowledge, performance details and selection guide
4) Basic knowledge, architecture, performance and selection of network processors
5) Basic knowledge and performance of common bus
6) Detailed performance introduction, design points and selection of various memories
7) Basic knowledge of physical layer interface chips commonly used in Datacom and Telecom, performance, design points and selection
8) Common device selection points and essence
9) Detailed performance introduction, design points and selection guide of FPGA, CPLD and EPLD
10) VHDL and VerilogHDL
11) Network Foundation
12) Hardware research and development process of domestic large-scale communication equipment company
2. Proficiency in and use of the industry's latest and most popular professional design tools1) ViewDraw, PowerPCB, Cam350
2) OrCad, Allegro; AD; PADS
3) Various circuit simulation tools
4) Learn to use VIEWDRAW, ORCAD, POWERPCB, SPECCTRA, ALLEGRO, CAM350, and other tools;
5) FPGA design tools, from various manufacturers.
First, the overall design of the hardwareStarting a hardware development project, the original driving force will come from many aspects, such as the needs of the market, based on the needs of the entire system architecture, the functional realization needs of the application software department, the need to improve the capabilities of some aspects of the system, etc., so as a hardware The designer of the system should take the initiative to understand the needs of all aspects, and put together to propose the most suitable hardware solution.
For example, the original driving force of the A project comes from a high-level software team within the company. They actually find that the original processor board IP forwarding capability cannot meet the requirements, which will cause great inconvenience to the system configuration and use. They raised the need for new hardware. According to this goal, two high-performance network processors are selected in the hardware solution, and then need to communicate with the software designer to determine the memory size, internal structure, number and type of external interfaces and debugging interfaces. Such details, such as software personnel like to completely separate the control signaling path and the data path, should be carefully considered when determining the direction of internal data.
At the beginning of the project, many discussion meetings are needed. All relevant departments should be invited to participate. There are three advantages. The first one can fully understand the needs of everyone, so as not to miss important functions in system design. The second is to let All departments understand the situation of this project, prepare for the time and cooperation on the staff early, and the third is emotionally speaking. At the beginning of the design, various departments have participated in it. This project has become a common brain for everyone. , will get everyone's care and good cooperation, is very helpful to complete the work.
Master the hardware design experience and design ideas necessary for the overall hardware design
1) Product demand analysis
2) Development feasibility analysis
3) System plan research
4) Overall architecture, CPU selection, bus type
5) Mainstream CPUs in the field of data communication and telecommunications: M68k series,
PowerPC860, PowerPC8240, 8260 architecture, performance and comparison
6) Overall hardware structure design and issues that should be noted
7) Communication interface type selection
8) Task decomposition
9) Minimum system design
10) PCI bus knowledge and specifications
11) How to avoid fatal errors during the overall design phase
12) How to properly perform task decomposition to achieve twice the result with half the effort?
13) Project case: medium and low-end routers, etc.
two. Hardware schematic design techniqueObjective: Through detailed project cases, detailed experience of schematic design, detailed design points and essence.
1) Principles and experience of mainstream CPU design in the field of telecommunications and data communication
2) The essence of the schematic design of Intel's PC motherboard
3) Network processor principle design experience and essence
4) Bus structure principle design experience and essence
5) Memory system principle design experience and essence
6) Principles and essence of the design of the general physical layer interface in the field of data communication and telecommunications
7) The principle design experience and essence of WATCHDOG commonly used in telecommunication and data communication equipment
8) Design experience and essence of the principle of hot plugging for telecommunication and data communication equipment systems
9) Crystal and clock system principle design experience and essence
10) PCI bus schematic design experience and essence
11) Project case: medium and low-end routers, etc.
Problems to be aware of in schematic design:
There must be "takenism" in the schematic design. Now the chip manufacturers can generally provide the schematic diagram of the reference design, so try to use these resources as much as possible to make some of your own play on the basis of fully understanding the reference design. When the main chip is selected, the most critical peripheral design includes the power, clock and inter-chip interconnects.
The power supply is the basis for ensuring the normal operation of the hardware system. The design should be analyzed in detail: the power input that the system can provide; the power output that the board needs to produce; the current that each power supply needs to provide; the efficiency of the power supply circuit; the allowable fluctuation of each power supply. Range; power-up sequence required for the entire power system, and so on. For example, the network processor in the A project requires 1.25V as the core voltage, the required accuracy is between +5% and 3%, and the current needs about 12A. According to these requirements, the design uses 5V power input, and uses the linear switching power supply. The controller and the IR MOSFET set up a suitable power supply circuit. The accuracy requirement determines the ESR selection of the output capacitor, and the remote feedback function is added to prevent the voltage drop caused by excessive current.
The realization of the clock circuit should take into account the jitter of the target circuit. The GE PHY device is used in the A project. At the beginning, a zero-delay clock distribution chip with a phase-locked loop is used to provide a 100MHz clock. The result is a GE link. There was a packet loss on it, and later it was replaced with a simple clock Buffer device to solve the packet loss problem. The analysis shows that the internal phase-locked loop introduces jitter.
The interconnection between the chips is to ensure the error-free transmission of data. In this respect, the high-speed differential signal lines have the characteristics of high speed, good wiring, good signal integrity, etc. The multi-chip interconnections in the A project use high-speed differential. Signal line, no problems in debugging and testing.
Need to be familiar with various level standards to ensure level matching.
three. Hardware PCB diagram designPurpose: Through the specific project case, all the experience of PCB design is revealed, so that you can quickly grow into an excellent hardware engineer.
1) High-speed CPU board PCB design experience and essence
2) Design points and essence of ordinary PCB
3) PCB design essence of PowerPC, ARM, MIPS, and single chip microcomputer
4) PCB design essence of Intel's PC motherboard
5) PCB design experience essence of PC motherboard, industrial computer motherboard, and telecom equipment motherboard
6) PCB design specifications and workflow of famous domestic communication companies
7) Relevant requirements for production and processing processes in PCB design
8) Transmission line problems in high speed PCB design
9) PCB design experience and essence of mainstream CPU (PowerPC series) in the field of telecommunications and data communication
10) PCB design experience and essence of general physical layer interface (100M, Gigabit Ethernet, ATM, etc.) in the field of telecommunications and data communication
11) PCB processor design experience and essence of network processor
12) The topology of the PCB step is extremely important
13) PCB design experience and essence of PCI step line
14) PCB design experience and essence of SDRAM, DDRSDRAM (125/133MHz)
15) Project case: mid-end router PCB design
Problems to be aware of in PCB design:
The purpose of PCB design is to be clear. For important signal lines, the length of the wiring and the processing of the ground loop are very strict, and for low-speed and unimportant signal lines, it can be placed at a slightly lower wiring priority. The important parts include: power supply segmentation; memory clock lines, control line and data line length requirements; high-speed differential line wiring and so on.
The memory chip used in the project realizes 1G DDRmemory. The wiring for this part is very important. It is necessary to take into account the topological distribution of control lines and address lines, the length difference control of data lines and clock lines, etc. According to the data sheet of the chip and the actual working frequency, specific wiring rules can be obtained. For example, the length of the data lines in the same group cannot differ by more than mil, and the length difference between each path cannot exceed more than mil. Wait. When these requirements are determined, the PCB designers can be clearly required to implement. If all the important wiring requirements in the design are clear, they can be converted into overall wiring constraints, and the PCB design can be realized by using the automatic routing tool software in CAD. It is also a trend in high-speed PCB design.
four. Hardware debuggingPurpose: To teach hardware debugging, testing experience and key points in specific project cases
1) Hardware debugging is equivalent to black box debugging. How to quickly analyze and solve problems?
2) the teaching of a large number of debugging experience;
3) How to speed up the hardware debugging process;
4) How to quickly solve the hardware debugging problem;
5) CE test requirements for DATACOM terminal equipment.
When preparing to debug a board, be sure to carefully check the visual inspection to see if there are visible short circuits and pin-stitching problems during the soldering process. Check if there are any component types placed incorrectly. Place errors, leak assembly, etc., and then use a multimeter to measure the resistance of each power supply to the ground to check for short circuits. This good habit can avoid damaging the board after powering up. In the process of debugging, we must have a peace of mind. It is very normal to meet the problem. What we need to do is to do more comparison and analysis, and gradually eliminate possible causes. We must firmly believe that "everything has a solution" and "the problem arises." There are reasons for it, so that in the end it will be able to debug successfully.
Fives. Hardware and software joint debugging1) How to judge the fault of the software?
2) How to jointly debug with the software?
3) A large number of joint debugging experience.
to sum up:Now from a technical point of view, each design can be made in the end, but the success of a project depends not only on the technical implementation, but also on the time of completion, the quality of the product, and the team's cooperation. Therefore, good teamwork, transparent and honest project communication, careful research and development arrangements, and sufficient materials and staffing arrangements can ensure the success of a project.
A good hardware engineer is actually a project manager. He/she needs to get the needs of his own design from the outside world, and then summarize and analyze it into a concrete hardware implementation. Also contact with a number of chip and solution providers to select the appropriate solution. When the schematic is completed, he/she will organize colleagues to cooperate with the review and inspection, and work with the CAD engineer to complete the PCB design. . At the same time, you should also prepare the BOM list, start purchasing and preparing materials, and contact the processing factory to complete the board placement. In the process of debugging, he/she should organize the software engineers to solve the problems together, cooperate with the test engineers to solve the problems found in the test, and wait until the products are launched to the site. If problems arise, they need to be supported in time. Therefore, a hardware designer should develop good communication skills, face the ability to adjust pressure, handle the coordination and decision-making ability of multiple affairs at the same time, and a good peace of mind.
skill requirements
There is also care and seriousness, because a small negligence in hardware design often causes very large economic losses. For example, when a board is encountered before, when the PCB design is complete, the wrong operation causes the power layer and the ground layer to be connected. Together, after the PCB board was manufactured, it was not checked directly on the production line. When the test was completed, the short circuit problem was found, but the components were all soldered to the board, resulting in hundreds of thousands of losses. Therefore, careful and serious inspection, responsible testing, unremitting learning and accumulation can make a hardware designer continue to make progress, and then the surgery industry has achieved a small success.
An important feature of engineering development is “stepping on the footprints of predecessorsâ€. Through the past few hundred years of engineering practice, there are many empirical data and experience methods for various situations. For example, for PCBlayout, basically every company All have their own designguidelines/checklist, which is what the company has summarized in many projects in the past. Each one can be said to have paid the price of "blood", which is for the board design; for the core chips and devices, Even more so, a chip or device that has been produced by hundreds of hundreds of people in a chip or device company for a few years can be thoroughly understood by hundreds of pages of datasheets.
In most cases, knowing the main interfaces, parameters, functions, and performance is sufficient, especially the designguidelines or applicationnotes provided by the chip/device company. These are generally the words of the chip/device engineers. In general, there is no one. Engineers with ten or twenty years of work experience can't write these things. It seems to be very simple, it seems to be nonsense, but a detailed analysis, combined with the circuit theorem and the electromagnetic law, a little analysis, you will find the word. Good students who have just graduated (usually learn well, like to solve problems, have strong learning ability and strong curiosity). When they start the hardware design, they will find that there are too many knowledge points and technical points involved. If this knowledge point wants to understand Thorough, the knowledge point should be understood thoroughly, and you will find that 24 hours a day is not enough, but I am sorry, the company invited you to come over is not for you to learn, is to do hardware design, you will see the schematic after a month, you Still holding an OrCAD manual command, a command to learn OrCAD use skills, research to have a serial resistance, study this capacitor is 0.1uF or 0.01uF.
It is a good thing to have curiosity, but it is in the spare time, in addition to the project, humbly learning from the older generation, try to use all kinds of designguidelines, complete the design work as soon as possible, record your own knowledge shortcomings, study hard in your spare time, understand thoroughly, through Design verification/testing to deepen the understanding of knowledge points is the right way to work.
When I graduated, I was delighted to find that the transmission line theory was too important. I spent a month working on the theory of transmission lines and deducing a large number of formulas for verification. In fact, it is a few words, impedance matching, if the receiving end If the impedance is greater than the transmitting end, what will happen to the signal; if it is less, what will happen to the signal; if it is open, what will happen if it is open; if it is short-circuited, what will happen, these basics will be introduced in the book of signal integrity, and will not There are very complicated mathematical formula derivations, knowing it, and then how to balance the impedance of the transmitter, serial resistance, PCB impedance, matching impedance, etc., are simple mathematical formulas.
All kinds of technologies/standards/chips/devices on hardware design must be known, when needed, can be handy, functional performance, parameter characteristics, advantages and disadvantages.
1. Ability to learn quickly:
On the one hand, communication technology, standards, and chip updates are too fast, so fast that you don't have time to understand the system, you can only understand through specific projects and needs; on the other hand, for the company, the hardware products that need to be done are also The change is very fast, customers need T1, E1, PDH, SDH, Ethernet, VoIP, Switch, Router, no one knows everything, they need to be able to combine the customer's needs, select the chip solution for detailed understanding, especially for the interface protocol. And electrical characteristics.
2. Understanding of communication protocols and standards:
Communication equipment, as its 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, etc.) Communication equipment, various circuits, PCB boards, and power supplies are all used for communication protocols.
Communication protocols are generally implemented by chips, either mature ASICs or FPGA/CPLDs developed by themselves. Chip engineers or FPGA engineers are closer to communication protocols than hardware engineers. They need to understand communication protocols very well and implement various logics. The state machine on it and the electrical parameter standards that meet the protocol. According to the seven-layer model of OSI, hardware engineers especially need to focus on the protocol standard of one physical layer and two layers of data link layer. With Ethernet distance, the physical layer is completed by PHY/transceiver chip, and the data link layer is MAC/ The switch chip is completed. For hardware engineers engaged in Ethernet related development, it is necessary to understand the PHY and Switch chip thoroughly, from coding mode, electrical parameters, eye diagram standard, template, signal frequency to frame format, forwarding processing logic, VLAN, etc. . This is especially true for traditional PDH/SDH/SONET devices. PDH/SDH/SONET is a more hardware device, meaning that the main protocols are implemented through ASICs. The functions of the software are mainly management, configuration, monitoring, alarm, performance, For hardware engineers, you must be familiar with the relevant protocols and interface standards used, especially for electrical specifications, eye diagram templates, so that you can be confident in design verification.
3. Ability to write documents:
As with software design, good software design requires good design documentation, clear requirements, what functions are implemented, and what acceptance criteria are achieved. As the integration of the chip increases, the interface rate increases, the complexity of the board increases, and the hardware design It is also becoming more and more complex and corresponding to the requirements of thermal stability, reliability, electromagnetic compatibility, and environmental protection, it is not through Xiaomi. The guerrilla warfare of the warehouse can be solved. Every hardware project is a war. It needs good planning and good analysis. This requires good documentation.
For hardware engineers, there are two most important documents: one is the hardware design specification (HDS: hardware design specification) and the hardware test report (generally called EVT: EngineeringValidation & Testreport or DVT: DesignValidation & Testreport). The requirements for HDS are detailed and clear. Main chip selection/hardware initialization, CPU selection and initialization, interface chip selection/initialization/management, block diagram (BlockDiagram) between each chip, DRAM type/size/speed, FLASH type/size/speed, chip select , interrupt, GPIO definition, reset logic and topology, clock/crystal selection/topology, RTC usage, memory map relationship, I2C device selection/topology, interface device/line definition, LED size/color/ Drive, heat sink, fan, JTAG, power topology / timing / circuit, etc.
For DVT, the requirements are simple and complex: what interfaces, chips, main components, circuits, and what to test on the board, especially when the board is working properly, power/voltage/ripple/timing, Eye diagram/template of the service interface, signal integrity and timing of the internal data bus (eg MII, RGMII, XAUI, PCIe, PCMbus, TelecomBus, SERDES, UART, etc.), CPU subsystem (eg clock, reset, SDRAM/DDR) , FLASH interface).
Good hardware engineers, whether they are doing documentation or reports, are easy to see, what solutions and circuits are needed for this hardware system, and finally verify the results of the tests. The content is detailed, not missing all kinds of interfaces/circuits; simple name, not nonsense; pictures and texts, when needed, a timing diagram, an oscilloscope capture can explain the problem.
4. Instrument/software usage:
Instruments include electric soldering iron, multimeter, oscilloscope, logic analyzer, BER tester, transmission analyzer, Ethernet tester Smartbits/IXIA, calorimeter, attenuator, optical power meter, RF signal strength meter, etc.; software includes Office ( Outlook, Word, Excel, PowerPoint, Project, Visio), PDF, commonly used schematic software Pads or OrCAD, commonly used PCB software Pads or Allegro, AllegroViewer, circuit simulation software PSPICE, signal simulation software HyperLynx and so on.
Both instrumentation and software, in political economy, are production tools that promote productivity. As hardware engineers, these instruments and software are the hands of wood. A cannon, a large part of the hardware engineer's ability to reflect the use of instruments and software, especially for the use of schematic software and oscilloscopes, the use of schematic software is a concrete implementation of hardware design, through a The placement of devices and the connection of NETs constitute a very complicated hardware logic software. It is the core work of the entire hardware design. The losses caused by mistakes and errors on any schematic are huge. , warfare."
In addition, the use of schematic software is also reflected in the aesthetics of the schematic, good design, simple and clear, clear notes, no matter who, along the line of thinking can quickly figure out the design intent, need special attention, not good The design, the East one device, the West one device, no logic, the name is weird, difficult to understand, it is quite troublesome to maintain in the future; the oscilloscope is the most important for the hardware engineer in all the test instruments, no matter the schematic or the PCB are the design Work, but any design requires careful verification testing, especially in the signal, it requires a lot of oscilloscope work, will not use the oscilloscope correctly, can not talk about the correct verification, the grounding is not connected, the choice of test points, trigger The choice of choice, the choice of delay, the choice of amplitude and time all determine the outcome of the test. If the wrong use of the oscilloscope will inevitably lead to erroneous test results, in this case, it may be that the wrong design is mistaken for correctness and brings a huge hidden danger; the correct design is mistaken for mistakes. Bring a lot of time and energy to waste.
5. Circuit design capabilities:
As chip integration increases, hardware design seems to be simpler. The first is the logical connection, followed by the serial resistor selection and parallel capacitor selection required for signal integrity, power supply filtering, and decoupling. But for a good hardware engineer, a simple logical connection (the output of the same bus of this chip is connected to the input of another chip, etc.) is only the most basic skills of hardware design, the circuit is the chip function, the communication protocol and various The carrier of the software does not have a deep understanding of the circuit. It does not have a deep understanding of the hardware design. Especially for the electrical performance parameters listed in the back of the chip or the understanding of various parameters of the discrete devices, it may be indiscriminately connected to the bus at 3.3V. It works, but now the working voltage has dropped to 1V. What is the concept, the noise on the signal line is so large that the sampling can be misjudged. As the signal rate increases and the operating voltage decreases, the digital signal has become more The analogy is more and more, which requires the PCB's impedance, capacitive reactance, inductive reactance, discrete devices (resistors, capacitors, inductors, diodes, transistors, MOSFETs, transformers, etc.), and the ASIC's interface electrical parameters are well understood. In-depth study of circuit principles, analog circuits and even electromagnetic field theory, circuits can be said to be a subset of electromagnetic field theory Without the understanding of electromagnetic field theory, there is no understanding of capacitance, inductance, crosstalk, and electromagnetic radiation.
Especially for the design of the power supply circuit, the voltage of the chip is now diversified, the voltage is getting lower and lower, and the current is getting larger and larger. The operator has strict requirements on the power consumption of the communication device, and the heat dissipation requirement is increasingly challenging for the power supply design. It can be said that for a hardware design, 40% of the work is based on the schematic/PCB design and post-test verification of the power supply circuit. The power supply circuit design is a concentrated expression of the hardware capability of the hardware engineer, various passive devices, semiconductor devices, Protection devices, DC/DC conversion typical topology, have many parameters, the formula needs to be considered and calculated.
6. Ability to communicate and globally control:
The hardware engineer is generally in the role of Teamleader in a hardware project. It is responsible for this hardware project. It is necessary to coordinate various resources such as PCB engineer, structural engineer, signal integrity engineer, electromagnetic compatibility engineer, and product manager, project. Managers, software engineers, production engineers, and procurement engineers work closely together to ensure that all aspects are step-by-step, and that the entire project plan needs to be understood, the release time of each sub-task, and the estimation of possible technical problems and risks.
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