Select 10 MCUs Step-by-step instructions

Source: Network Organization Posted in : 2021-09-26 16:23:29

Choosing the right microcontroller for a product can be a daunting task. Not only are there many technical features to consider, but there are also business case issues, such as cost and lead time, that can cripple a project. At the beginning of a project, it's quite possible to jump in and start selecting a microcontroller before the system details are finalized. This is of course a bad idea. Before considering a microcontroller, hardware and software engineers should develop a high-level, block diagram, and flowchart of the system, and then have enough information to start making a sound decision about microcontroller selection. When you get to this point, there are 10 easy steps to follow to make sure you make the right choice.

Step 1: List Required Hardware Interfaces< span style="font-family: Microsoft Yahei;color: #222222;font-size: 16px">
Step 2: Check software architecture

Software architecture and requirements can greatly influence the choice of microcontroller. The processing requirements will determine whether you use an 80 MHz DSP or an 8 MHz 8051. Just like with hardware, take note of any important requirements. For example, are there any algorithms that require floating point math? Are there any high frequency control loops or sensors? Estimate how long and how often each task needs to run. Get an order of magnitude sense of how much processing power is required. The required computing power will be one of the biggest demands on microcontroller architecture and frequency.

 Step 3: Choose Architecture

Using the information in steps 1 and 2, engineers should be able to begin to understand the required architecture. Can an application use an octet architecture? How about 16 bit? Does it require a 32-bit ARM core? Between the application and the required software algorithm, these problems will begin to converge into a solution. Don't forget to keep in mind possible future requirements and feature creep. Just because you can use an 8-bit microcontroller today doesn't mean you shouldn't consider a 16-bit microcontroller for future functionality or even ease of use. Don't forget that microcontroller selection can be an iterative process. You can choose a 16-bit part at this step, but you'll find that a 32-bit ARM part works better in a later step.

Step 4: Determining memory requirements

Flash memory and RAM are two very critical components of any microcontroller. Making sure you don't run out of program space or variable space is definitely the highest priority. It is much easier to select a part with too many of these features than to select them. Getting to the end of the design and finding out that you need 110% or a feature that needs to be cut is not going to work. After all, you can always start with more and move on to a more limited part of the same chip family. Using the software architecture and communication peripherals included in the application, engineers can estimate how much flash and RAM the application will need. Don't forget to leave room for feature creep and the next release! It will save you a lot of headaches in the future.

Step 5: Start searching for microcontrollers

Now that you have a better understanding of the functions your microcontroller needs, it's time to start your search! A good place to start is a microcontroller supplier such as Arrow, Avnet, Future Electronics or similar. Discuss your application and requirements with the FAE, and they can often guide you to new parts that are at the forefront and meet the requirements. Keep in mind that they may be putting pressure on them to push a certain microcontroller family at the time!
The next best place to start is with a chip supplier you are already familiar with. For example, if you have used Microchip parts in the past and have a good experience with them, start with their website. Most chip suppliers have a search engine that allows you to enter peripheral sets, I/O, and power requirements, and it narrows down the list of eligible parts. The engineer can then proceed to select a microcontroller from this list.

Step 6: Check cost and power limits

At this point, the selection process has revealed many potential candidates. This is a good time to check the power requirements and cost of components. If the device is going to be powered by batteries and mobile, it's definitely not stable to make sure the parts are low power. If it doesn't meet the power requirements, keep clearing the list until you choose a few. Also don't forget to check the unit price of the processor. While volume prices for many parts are steadily approaching $1, if it's a highly absolutized or high-end machining machine, price can be critical. Don't forget this key element.

Step 7: Check Part Availability

With a list of potential parts in hand, now is a good time to start checking parts availability. Some things to keep in mind are what is the lead time for the parts? Are they stocked at multiple distributors or do they have lead times of 6 to 12 weeks? What are your requirements for availability? You don't want to be stuck with a large order and have to wait three months to complete. Then there's the question of how new the part is and whether it will last for the life of your product. If your product is going to be 10 years old, you need to find parts that the manufacturer guarantees will still be made for 10 years.

Step 8: Select Development Kit

One of the best parts of choosing a new microcontroller is finding a development kit to work with and understanding the inner workings of the controller. Once engineers have identified the parts they want to use, they should research available development kits. If the dev kit is not available then the selected part is most likely not a good choice and they should go back a few steps and find a better part. Most development kits today cost less than $100. Paying more (unless it's designed to work with multiple processor modules) is too much. Another part might be a better option.

Step 9: Research compilers and tools

 The choice of development kits almost solidifies the choice of microcontrollers. A final consideration is to check the available compilers and tools. There are a variety of compilers, sample code, and debugging tools to choose from for most microcontrollers. It is important to ensure that the part has all the necessary tools. Without the right tools, the development process can become tedious and expensive.

Step 10: Start experimenting

Even with the choice of microcontroller, nothing is set in stone. Often, development kits arrive long before the first prototype hardware appears. Take advantage by building test circuits and connecting them to a microcontroller. Select high risk parts and have them work on the development kit. You may find some unforeseen issues with parts that you thought worked well, forcing you to choose a different microcontroller. Regardless, early experimentation will ensure you make the right choice and if changes are required, the impact will be minimal!