First, the basic principles of component selection:
a) Universality principle: If the selected components are widely used, they should use less cold gates and partial gate chips to reduce development risks.
b) Cost-effective principle: In the case of similar functions, performance, and usage rates, try to select components with better price and reduce costs.
c) Procurement convenience principle: Try to choose components that are easy to buy and have a short lead time.
d) Sustainable development principles: Try to choose components that will not be discontinued for the foreseeable time.
e) Alternative principle: try to choose more components with pin to pin compatible chip brands.
f) Upward compatibility principle: Try to select the components used in previous old products.
g) Resource saving principle: Try to use all the functions and pins of the components.
The chip selection process is a compromise for each dimension.
Second, the whole process pays attention to the chip attribute 1. When we select the type, we need to consider the situation of trial production, and also need to consider the situation during mass production.
The price, delivery cycle, and sample application for small-volume purchases; at the same time, attention should be paid to the price and lead time after mass shipments. It is possible that after the batch has become larger, there is no advantage in the price of the supply, or the capacity is insufficient after the batch is large.
In addition, according to your actual purchase situation, find the corresponding level of supplier. For example, the original factory often does not supply directly, and needs to pass the agent. Some agents' supply levels are required.
Previously, there was a selection, and ST's STM32F427IGT6 was chosen. The original factory is very helpful to apply for samples. However, the difficulties encountered in the procurement process, although we hope to purchase the whole disk, but because of the certain requirements of its agent shipments, the price is inconsistent with the price that was originally learned by the original factory. It is much higher.
At the same time, because the whole industry uses the chip, there are not many scenes, so the price of Taobao is very expensive, and there is no way to accept it. At the same time, a friend who has done chip sales said that it was due to the heavy use of drone manufacturers, which led to the price of this chip, which made it difficult to buy.
2. Pay attention to the match between the life cycle of the device itself and the product life cycle. For communication devices, the devices we choose generally have a life cycle of more than 5 years, and there are follow-up complete product development roadmaps.
At the time of our new hardware platform, the product was planned to replace the mature platform with a shipment volume of one million boards. Because the switching period is relatively long. The new product will gradually increase after 1~2 years after the completion of development. One of the DSP boards, the peripheral storage is SDRAM. At the time when the product was ready for paving, several major memory chip manufacturers, such as Magnesium, announced that they would stop production. As a result of the product being just loaded, a large number of stock chips were hoarded, and small factories in Taiwan were sought for device replacement.
Therefore, when the device is selected, it fully embodies that "people must have near-worry without long-term consideration."
3. In addition to considering the functional and laboratory environment, you also need to consider the entire life cycle scenario.
Third, the specific selection, processor selection <br> To choose a processor, there are many factors to consider, not only pure hardware interface, but also need to consider the relevant operating system, supporting development tools, simulator , as well as the experience of the engineer's microprocessor and software support.
Considerations for Embedded Microprocessor Selection In product development, as a core chip microprocessor, its own functions, performance, and reliability are expected to be high, because its resources are richer, its own functions are more powerful, product development The shorter the cycle, the higher the success rate of the project. However, any microprocessor can't be perfect to meet the needs of each user, so this involves the problem of selection.
(1) Application field Once the function and performance of a product are customized, the application field of the product is also determined. The determination of the application field will narrow the scope of the selection. For example, the working conditions of the products in the industrial control field are usually harsh, so the operating temperature of the chip is usually wide temperature, so that the industrial grade chip is selected, and the civilian grade is selected. Excluded. At present, the more common application areas are classified into aerospace, communications, computers, industrial control, medical systems, consumer electronics, automotive electronics and so on.
(2) Self-contained resources often see or hear such questions: What is the main frequency? Is there a built-in Ethernet MAC? How many I/O ports are there? Which interfaces are included? Support online simulation? Is it supported? OS, which OS can be supported? Is there an external storage interface?... The above all involve the issue of chip resources. What kind of resources the microprocessor comes with is an important consideration in the selection. The closer the chip comes with the resources, the simpler the product development.
(3) Scalable resources The hardware platform must support OS, RAM and ROM, and the requirements for resources are relatively high. Chips generally have built-in RAM and ROM, but their capacity is generally small, built-in 512KB is very large, but running OS is generally more than mega-level. This requires a chip to expand the memory.
(4) Power consumption Single look at "power consumption" is a relatively abstract term. Low-power products are energy-efficient and cost-effective, can even reduce environmental pollution, and increase reliability. It has so many advantages, so low power consumption has become an important indicator in chip selection.
(5) Packaging Common microprocessor chip packages mainly include QFP and BGA. BGA type package soldering is troublesome, and ordinary small companies will not solder, but the chip size of BGA package will be much smaller. If the product does not require strict chip size, it is best to choose QFP package when selecting.
(6) The continuity of the chip and the inheritability of the technology At present, the speed of product replacement is very fast, so the scalability of the chip should be considered in the selection. If it is the chip of the same core series of the same manufacturer, its technology inheritability is better. You should consider a well-known semiconductor company, and then query its related products, and then make a judgment.
(7) Price and supply guarantee The price and supply of the chip are also factors that must be considered. Many chips are currently in the trial stage, and their price and availability will be unstable. Therefore, try to choose a chip with mass production.
(8) The emulator emulator is a tool to be used when debugging hardware and low-level software. If it is not in the early stage of development, it will basically be difficult. Choosing the right emulator will bring a lot of convenience to development. For those who already have an emulator, consider whether it supports the selected chip during the selection process.
(9) OS and development tools As product development, it is necessary to consider the support of the software when selecting the chip, such as what kind of OS is supported. For those who have an OS, it is necessary to consider whether the selected chip supports the OS during the selection process, or vice versa, whether the OS supports the chip.
(10) Technical support The current trend is to buy services, that is, to buy technical support. The technical support ability of a good company is relatively guaranteed, so it is best to choose a well-known semiconductor company when selecting chips.
In addition, the maturity of the chip depends on the size and usage of the user. Choosing a wider range of chips on the market will have more shared resources and bring a lot of convenience to development.
Here again, some manufacturers are good at making simple applications of MCUs, and some manufacturers are good at industrial control or more complex MCU and CPU applications, so there will be advantages and disadvantages.
CPU according to the instruction set architecture system is divided into PowerPC, X86, MIPS, ARM four, X86 uses CISC instruction set, POWERPC, MIPS, ARM uses RISC instruction set, RISC CPU is mostly used for embedded.
The industry's PowerPC is mainly used in the network communication market. The X86 focuses on the PC and server markets. The MIPS target market is embedded applications such as networking and communication, and digital consumer applications. ARM's target market is portable and handheld computing devices, multimedia, and digital consumption. Class products.
In the high-end processor, the x86 architecture dual-core processor and the MIPS architecture multi-core processor have different service orientations. The MIPS processor is easy to implement multi-core and multi-thread operations, and performs well in data plane message forwarding, but the single processor core structure is simple. It is obviously not as good as x86 and PowerPC for complex operations and message deep processing. The data processing uses multi-core MIPS or NP, and the control application selects PowerPC or embedded x86.
ARM industry's industry ecological environment is better, there are a number of chip suppliers can provide ARM devices, the selection must undergo a number of comparative analysis and competitive evaluation.
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