1. Embedded product development process

Embedded products, like ordinary electronic products, need to follow some basic processes in the development process, which is a process from demand analysis to overall design, detailed design to final product completion. However, compared with ordinary electronic products, the development process of embedded products has its own special features. It contains two parts: embedded software and embedded hardware. The development of embedded hardware and software does not need to be involved in the development process of ordinary electronic products. The specific development process of embedded products is as follows:

Below, we will discuss in detail the various stages in the development process of embedded products:

Stage 1: Product Requirements

At this stage, what we need to figure out is where the demand for the product comes from, and what needs we need to meet for a successful product. Only when the needs are clear can our product development goals be clear. In the product requirements analysis stage, we can obtain product requirements through the following channels:
1) Market analysis and research, mainly to see what the market demand is, and what the cutting-edge technology is (from the perspective of making a product);
2) Customer research and user positioning to obtain the most accurate product needs from customers in the market (pay attention to analyzing the market, product life cycle, and whether upgrades are convenient);
3) Profit orientation (cost budget);
4) If it is an outsourcing project, our customers need to provide product requirements (obtain them directly from the customers and have them sign the agreement);
When a project is completed, if customers suddenly increase their demands and add functions, your project cycle will be seriously delayed and costs will rise dramatically. In addition, all tested products may need to be retested, and the original design may not meet the requirements. Current requirements, so before starting a project, it is best to determine the requirements with the customer and sign an agreement. Otherwise, no matter how many days and nights you work hard, you will end up with an unmanageable mess!

Stage 2: Product Specification

In the previous stage, we collected all the requirements for the product. So in the product specification stage, our task is to refine all the requirements into specific specifications of the product. For example, for a simple USB to serial port cable, we need to determine the product specifications, including:
1) Appearance of the product;
2) Operating systems supported by the product;
3) Product interface form and supported specifications;
Etc., etc., remember that after forming the product specifications, we must strictly abide by them in the subsequent development process. We cannot change the product requirements at will without 200% reason. Otherwise, the product development process will be an iterative process.
The "Product Specifications" mainly consider the following aspects:
1) Consider what hardware interfaces the product requires;
2) In what environment will the product be used, how big will it be, and how much power will it consume? If it is a consumer product, it also depends on the beautiful design, whether the product is easy to carry, the size of the board, and whether it is waterproof;
3) Product cost requirements;
4) Explanation of product performance parameters (for example, a switch, if it has a rate of 100 Mbit/s, is used in homes and general companies; if it is used for switching in the entire province, the designed rate must be hundreds of thousands of Mbit/s or more). Therefore, the product Differences in performance parameters will affect our design considerations, so the product specifications will naturally be different;
5) National standards, international standards, or industry standards that need to be adapted and complied with;

Stage 3: Overall product design plan

After completing the product specifications, we need to understand what feasible solutions are currently available for this product, compare several solutions, including considering cost, performance, development cycle, development difficulty and other aspects, and finally choose one The overall product design plan that best suits you.
At this stage, in addition to determining the specific implementation plan, we also need to comprehensively consider the product development cycle, how many man-months of work will be required, what resources or external assistance are needed, as well as the risks and countermeasures that may be encountered during the development process. , form the project plan for the entire project and guide our entire development process.

Stage 4: Product Outline Design

Product outline design is mainly based on further refinement of the overall design plan, specifically starting from both hardware and software aspects:
Hardware module outline design
The outline design of hardware modules mainly starts from the perspective of hardware, confirms the architecture of the entire system, divides each module according to function, and determines the approximate implementation of each module. First of all, we must select the CPU based on what peripheral functions we want and the work the product needs to complete (note: once the CPU is determined, your surrounding hardware circuits must be designed with reference to the circuit scheme provided by the CPU manufacturer). Then select the chip based on the functional requirements of the product, such as whether to use an external AD or an on-chip AD, what communication method to use, what external interfaces are available, and most importantly, electromagnetic compatibility should be considered.
Generally, the life cycle of a CPU is 5-8 years. When you are considering selection, you should pay attention not to choose a CPU that is about to be discontinued, so as to avoid such an ending: the product has been developed for 1 to 2 years, and it has just been developed. Before making any money, the CPU was discontinued and had to be developed again. Many companies die from this.
Software module outline design
The software module outline design stage mainly divides the entire system into modules according to functions according to the system requirements, and defines the interfaces between each functional module, as well as the main data structures within the modules.

Stage 5: Product Detailed Design

Detailed design of hardware modules
Mainly the specific circuit diagram and some specific requirements, including parameters such as the mutual design of the PCB and the shell, and the size. Next, we need to complete the design of the entire hardware according to the guidance of the hardware module detailed design document. Including schematic diagram and PCB drawing.
Detailed design of software modules
Definition of functional function interface, which completes functions, data structures, global variables, and the calling process of each functional function interface when completing tasks. After completing the detailed design of the software module, the specific coding stage is entered. Under the guidance of the detailed design of the software module, the software coding of the entire system is completed.
It must be noted that the detailed design document of the module needs to be completed before the software enters the actual coding stage and the hardware enters the specific schematic and PCB implementation stage. This way, it is possible to consider everything thoroughly at the beginning of the design and avoid repeated modifications during the design process. To improve development efficiency, do not start the actual design steps without completing the detailed design just for the sake of a quick drawing.

Phase 6&7: Product Debugging and Verification

This stage is mainly about adjusting the hardware or code, correcting existing problems and bugs, so that it can run normally, and trying to make the product's functions meet the product requirements and specifications.
Hardware parts:
1) Visual inspection of the PCB during processing will determine whether there is a short circuit on the PCB board, whether the components are soldered incorrectly, or whether there is missing soldering;
2) Test whether the resistance of each power supply to ground is normal;
3) Power on and test whether the power supply is normal;
4) To debug hardware modules by modules, you can use oscilloscopes, logic analyzers, etc.
Software part:
Verify whether a single function of the software is implemented, and verify whether the entire product function of the software is implemented.

Phase 8: Testing

Functional test (if the test fails, there may be a BUG);
Stress test (if the test fails, there may be a BUG or the parameter design is unreasonable);
Performance testing (product performance parameters should be extracted for future customer reference, this is part of your product features);
Other professional tests: including industrial-grade tests, such as anti-interference test, product life test, moisture resistance test, high temperature and low temperature test (some products do not work properly at very high temperatures or very low temperatures, or even stop working) .
Some equipment's electronic components will have abnormal parameters at special temperatures, causing the entire product to malfunction or malfunction; some equipment will not start or turn on at all when the temperature is tens of degrees below zero; some When the equipment is exposed to high temperatures, the capacitance or resistance values will undergo physical changes, which will affect the quality of the product. Here is a topic: What is the difference between industrial-grade products and consumer products? Industrial-grade products must avoid these anomalies and special problems. Some products work in deep seas, cold caves, hot deserts, or on bumpy equipment, such as cars; or need to be protected from lightning strikes. ; So this is the difference between industrial products and consumer products. Consumer products do not need to undergo so many tests.

Stage 9: Product

After passing the complete test and verification in the previous stage, at this stage, we will have a successfully developed product. At this stage, you can compare the actual product with the initially formed product specifications to see if, after a complete development process, the product fully complies with the original product specifications, or if problems with the product specifications are discovered midway, make adjustments to it. How many modifications have been made?

Appendix: Embedded hardware development process

Previously, we described the development process of embedded products in detail. In this section, we will take the hardware part of embedded products as an example to explain the development process again. We hope that through this section, everyone can understand the development of embedded hardware. Have a deeper understanding of the process, and in future studies and work, it will be more standardized and standardized, and development skills will be improved. The embedded hardware development process is generally as shown below, divided into 8 stages:

The hardware forms of embedded products vary, with CPUs ranging from simple 4-bit/8-bit microcontrollers to 32-bit ARM processors and other special-purpose ICs. In addition, depending on the different needs of the product, the peripheral circuits are also different. In every hardware development process, it is necessary to consider various factors based on actual needs and select the most appropriate solution.

Hardware Phase 1: Hardware Product Requirements

The requirements are the same as those for ordinary embedded products. Stage 1: Product requirements.

Hardware Phase 2: Overall Hardware Design Plan

For a hardware development project, its needs may come from many aspects, such as market product needs or performance improvement requirements. Therefore, as a hardware designer, we need to take the initiative to understand and analyze the needs of various aspects, and according to what the system needs to complete function, choose the most appropriate hardware solution.
At this stage, we need to analyze the feasibility of the entire system design, including the procurability of the main components in the solution, product development investment, project development cycle estimation, development risk assessment, etc., and address problems that may be encountered during the development process, Choose a response plan in advance to ensure the smooth completion of the hardware.

Hardware Phase 3: Hardware Circuit Schematic Design

After the system scheme is determined, we can carry out relevant design work. The principle design mainly includes the overall system design and detailed design, and finally produces detailed design documents and hardware schematic diagrams.
Principle design and PCB design are one of the two most important tasks for designers. During the principle design process, we need to plan the internal resources of the hardware, such as system storage space, and the implementation of each peripheral circuit module. In addition, the main peripheral circuits of the system, such as power supply, reset, etc., also need to be carefully considered. In some high-speed designs or special applications, EMC/EMI, etc. also need to be considered.
Power supply is the basis for ensuring the normal operation of the hardware system. Detailed analysis is required in the design: the power input that the system can provide; the power output that the single board needs to generate; the current size that each power supply needs to provide; the efficiency of the power supply circuit; and the fluctuations that each power supply can allow. Scope; power-on sequence required by the entire power system, etc.
In order for the system to work stably and reliably, the design of the reset circuit is also very important. How to ensure that the system will not reset abnormally due to external interference, how to ensure that the system can be reset in time when the system runs abnormally, and how to reset reasonably can ensure that the system Complete reset, these are also things we need to consider when designing the principle.
Similarly, the design of the clock circuit is also a very important aspect. A poor clock circuit design may cause data packet loss in communication products, generate large EMI, and even cause system instability.
There must be "use-ism" in schematic design! Today's chip manufacturers can generally provide schematic diagrams of reference designs, so you should try your best to make use of these resources and do some work of your own based on a full understanding of the reference designs.

Hardware stage 4: PCB diagram design

The PCB design stage is to convert the schematic design into an actual processable PCB circuit board. Currently, the mainstream PCB design software includes PADS, Candence and Protel.
PCB design, especially high-speed PCB, needs to consider EMC/EMI, impedance control, signal quality, etc., which places higher requirements on PCB designers. In order to verify whether the designed PCB meets the requirements, some also need to perform PCB simulation. And adjust the PCB layout and routing based on the simulation results to complete the entire design.

Hardware stage 5: PCB processing file production and PCB proofing

After the PCB drawing is completed, at this stage, we need to generate a processing file that can be recognized by the processing factory, which is often called a light drawing file, and hand it to the processing factory for proofing the PCB blank board. Generally, proofing of 1 to 4-layer boards can be completed within a week.

Hardware Stage 6: Welding and debugging of hardware products

After getting the blank PCB board sampled from the processing factory, we next need to check whether the blank PCB board is as expected in our design and whether there are obvious short circuits or breaks. After passing the inspection, we need to transfer the previously purchased components and The empty PCB board is handed over to the manufacturer for welding (if the PCB circuit is not complex, in order to speed up the process, the components can also be welded directly by hand).
After the PCB has been soldered, before debugging the PCB, you must first carefully check whether there are visible short circuits and pin soldering faults, check whether there are incorrect placement of component models, incorrect placement of the first pin, missing assembly, etc. Then use a multimeter to measure the resistance from each power supply to ground to check whether there is a short circuit. This can avoid damaging the board after powering on hastily. During the debugging process, you must have a peaceful mind. It is very normal to encounter problems. What you need to do is to do more comparison and analysis, and gradually eliminate possible causes until the final debugging is successful.
During the hardware debugging process, frequently used debugging tools include multimeters, oscilloscopes, logic analyzers, etc., to test and observe the signal voltage and signal quality within the board, and whether the signal timing meets the requirements.

Hardware Phase 7: Hardware Product Testing

After the hardware product is debugged, we need to compare it with the product's requirement description and test one by one to confirm whether it meets the expected requirements. If the requirements are not met, the hardware product needs to be debugged and modified until it meets the product requirements. (Generally, the requirements description document is used as the criterion, except of course for obvious requirements description errors).

Hardware Stage 8: Hardware Products

The hardware we ultimately developed was successful. A complete hardware product that meets product requirements cannot yet describe a successful product development process. We also need to complete it on time and with high quality according to the scheduled plan. This is a successful product development process.