Hardware Design Process

The development process of a product is a complicated and highly technical job, and a stable and reliable hardware platform with excellent performance is the foundation and guarantee of the company's product quality. Therefore, the process of hardware design work should follow certain standards and norms in order to meet the requirements of quality assurance. This paper focuses on the specification process of hardware design. It mainly includes the following contents: confirmation of hardware requirements, hardware system design, schematic diagram design, PCB design, prototype joint debugging and testing, project review and case closing.

1. Confirmation of hardware requirements

Before developing a product, first confirm the hardware requirements of the product. This information is usually provided by the customer in a very detailed document, and the business department of the company conveys the requirements to the development department. It is very important to understand user needs, because subsequent product solution selection, development plans, product inspection standards and other information come from this. This information includes: the target market for product application; all functions and performance standards that need to be met; the appearance size, mold and accessories of the product; the time of product demand.

2. Hardware system design

Hardware system design, including selection of overall solution; confirmation of product mold appearance; formulation of project plan. According to customer needs, such as CPU processing power, storage capacity and speed, function and interface requirements, etc., select the appropriate overall solution. And to complete the selection of design schemes for key functional modules, the selection of key components, technical data, technical channels and technical support, fully consider technical feasibility, reliability and cost control. The selection of key components should follow the following principles:

Unity: key function module devices, in the case of meeting the functional and performance requirements, try to choose module devices that have been used in other solutions within the company, and try to ensure the unity of peripheral circuits.

Versatility: Try to choose pin to pin compatible components with a wide variety of components, as well as chips that have been widely used and verified in the market, and try to avoid choosing unpopular chips to reduce design risks.

High cost performance: In the case of meeting the demand, try to choose low-cost components.

Convenient procurement: Try to choose components that are convenient to purchase, have a short delivery period, and have no plans to stop production. The selection and design of molds should be as far as possible from the user's point of view, aesthetics, durability, safety, heat dissipation, cost, etc. are all issues that need to be considered. This work needs to be completed jointly by hardware engineers, structural engineers and art engineers. A realistic and rigorous project plan is a guarantee for product development in terms of time and efficiency. The project plan should not only take into account various uncertain factors that may arise, reasonably arrange the time schedule of each stage, but also ensure the work efficiency of the project personnel during the development process, so as to ensure that the product development is within the time required by the customer, and the quality and quantity are guaranteed in advance the completion.

3. Schematic design

The design of the schematic diagram is fundamental to ensure the logical correctness of a product hardware. If there is a problem with the schematic design, it will cause the performance of some functional modules of the product to deteriorate or fail, and the system will be unstable or even unable to work if it is serious. The things to pay attention to in schematic design are roughly summarized as follows:

When drawing the schematic diagram, try to use the company's standard component library package, and try to use the company's unified plan for the general function module design. The standardized schematic diagram design is easier to manage and review, and facilitates procurement and production control.

General rules for schematic diagram design: According to the target market, determine the protection level of the schematic diagram for the part of the circuit that needs to be protected.

Power supply system: At the beginning of the design, it is necessary to analyze in detail the current size required by each power supply in the board, accuracy requirements, ripple control, power-on sequence, etc. The design of the power supply must have sufficient margin, otherwise it will easily cause problems such as excessive heat generation of the power chip, insufficient output capacity of the power module, and malfunction of the system. Attention should also be paid to the separation of digital power and analog power.

Cost control: Generally speaking, the greater the redundancy in the design, the more reliable the system will be, but the higher the cost will be; conversely, the smaller the redundancy will be, the lower the cost will be but the lower the reliability will be. The first version of the schematic diagram can reserve high design redundancy to ensure the stability of the system. At the same time, some compatible designs can be made to facilitate the cost reduction test in the subsequent debugging process, and finally achieve the most appropriate redundancy to make the product more cost-effective. optimize.

Review: After the schematic design is completed, it needs to be sent to the chip provider for review, and the key modules are sent to the chip manufacturer for technical support review. The company should also organize strict review, especially for newly added functional modules, carefully review and demonstrate, in order to Ensure the correctness of the schematic diagram.

Write design documents: 10-port connection methods related to software debugging, control status requirements, device addresses connected to the bus, etc., to facilitate subsequent software debugging.

BOM production: Export the list of components, and make a BOM list according to the company's BOM standard format, indicating the code, type, detailed description, accuracy level, package size, assembly method, single-machine consumption, and bit number of each device. After completion, submit the sample plan quantity to the relevant personnel to check the inventory, and submit the purchase requisition if there is a shortage of materials. This part of the work should be done in advance, so as not to affect the development cycle due to the arrival time of materials.

4. PCB design

After the schematic diagram is completed, export the netlist and synchronize it to the PCB file. The packaging of PCB B should adopt the company's standard packaging as much as possible, and the new device packaging should read the chip manual carefully. Before starting PCB drawing, first ensure the correctness of all component packages.

1. General steps and precautions of PCB design

According to the selected mold, confirm the size of the motherboard, the position of all connectors related to mold assembly, height restrictions, areas where devices are prohibited, etc.

Layout: The first principle of layout is to ensure the routing rate of the wiring, and place the devices of certain functional modules together as much as possible, but the interconnection between chips should pay attention to which devices should be placed close to which chip; digital devices and analog devices should be Separate and keep as far away as possible; heat-sensitive devices should be placed away from heat-generating devices; devices and wiring should not be placed near the positioning holes; decoupling capacitors should be as close as possible to the V c C of the device; when placing devices, consider subsequent debugging and soldering, not too dense; Consider the aesthetics of the entire board.

2. General rules for wiring

Clock line and high-speed signal line: clock line and high-speed signal line are generally easy to be the interference source of electromagnetic radiation, so special attention should be paid to wiring. Generally divided into single-ended and differential. Generally, the single-ended line should be as short as possible, the formation or reference layer should be as complete as possible to reduce the loop, the ground cover should be complete and more ground holes should be drilled; the differential line should be complete in formation or reference layer, with equal length and equal distance. If there is an impedance requirement, the line width and line spacing should be calculated to reduce radiation.

Important signal lines: pay attention to the treatment of ground cover, formation integrity and impedance control.

Power line: According to the evaluation of the current of each power supply, the thickness of each power line can be set. Generally, the power line should be as thick as possible. The greater the current, the thicker the power line.

Ground wire: To ensure the integrity of the ground plane as much as possible, the ground wire should be as thick as possible.

Design inspection and review: After the P4 design is completed, use the inspection function that comes with the tool to check the spacing and connectivity to ensure that the spacing and connectivity are correct. Finally, after self-checking and optimization, send it to the chip provider to check the design, and send important modules to Corresponding technical support checks must also be carefully reviewed item by item within the company in accordance with standard procedures.

Template file output and production: After the PCB design is completed, a board-making instruction file must be produced, including board thickness, board material, surface treatment method, characters, solder mask, board size and whether to assemble boards, quantity, impedance, etc. There will be a company's standard format for printed board factory production. At the same time, provide BOM files, coordinate files and silk screen drawings to the chip factory for sample mounting and welding.

5. Sample joint debugging and testing

1. Model joint debugging

After the hardware schematic diagram is designed, provide the schematic design document to the software personnel, so that they can start modifying the software according to their own hardware design in advance. After the sample mounting is completed, the software personnel will be handed over to the final software development work. During this period, the necessary hardware debugging will be carried out in cooperation with the software work. After all the functions required by the customer are completed, the hardware engineer will complete the remaining testing and confirmation. Work.

2. Sample test

Testing work can generally be divided into functional testing, performance testing and debugging, on-site testing and customer confirmation, and third-party certification testing.

Taking the hardware requirements confirmation document as a guiding document, according to the requirements put forward by customers, hardware engineers conduct detailed tests and confirmations on all required functions and performance requirements, and perform software and hardware debugging for projects that do not meet the standards. The performance indicators not proposed by the customer are based on the relevant national standards and company testing standards.

After the hardware engineer's testing and debugging is completed, it is submitted to the company's internal testing, and the group does a confirmation test to confirm whether the product meets all standard requirements in the laboratory. Due to the possible complexity and particularity of the target market environment, after the product self-test is completed, testers need to go to the target market site to conduct on-site multi-site testing. At the same time, communicate with customers to allow customers to make final confirmation of the product. According to customer requirements, if a third-party certification body is required to test, a prototype needs to be provided to the third-party certification body for certification testing and a certification report.

6. Project review and closing

Organized by the project manager, the participants include the company's technical director, business personnel, software chief designer, hardware chief designer, testers and related senior technical personnel. Taking the technical requirements provided by customers as the guiding evaluation standard, and based on various internal design standards, testing standards, and auditing standards of the company, we conduct rigorous and detailed audits on various design documents, test reports and customer feedback of the project. Under the premise of ensuring that the product fully meets the customer's needs, evaluate and review the correctness, rationality, standardization, reliability and cost-effectiveness of the product design, and confirm whether the project meets the requirements and the case can be closed, and the relevant personnel participating in the project review Personnel sign and confirm one by one.

Judging whether a project is successful is not only based on whether a design meets the requirements technically, but also whether the design is reasonable, whether the quality of the product passes the test, whether the cost of the product is properly controlled, and whether the completion time meets the needs. This requires efficient teamwork, detailed demand analysis, accurate solution selection, reasonable project planning, standardized design documents and rigorous project review, and a perfect hardware design process can precisely make these well connected, and it is also The guarantee of a good product design.

The above is the hardware design and development process introduced by Shenzhen Zuchuang Microelectronics Co., Ltd. for you. If you have software and hardware function development needs for smart electronic products, you can rest assured to entrust them to us. We have rich experience in customized development of electronic products, and can evaluate the development cycle and IC price as soon as possible, and can also calculate PCBA quotations. We are a number of chip agents at home and abroad, including MCU, voice IC, Bluetooth IC and modules, wifi modules. We have hardware design and software development capabilities. Covering circuit design, PCB design, single-chip microcomputer development, software custom development, APP custom development, WeChat official account development, voice recognition technology, Bluetooth wifi development, etc. It can also undertake the research and development of smart electronic products, the design of household appliances, the development of beauty equipment, the development of Internet of Things applications, the design of smart home solutions, the development of TWS solutions, the development of Bluetooth audio, the development of children's toys, and the development of electronic education products.