The STM32 MCU from STMicroelectronics has evolved over more than a decade, resulting in numerous series and specifications, making it overwhelming for many users to choose from.
How complex are the STM32 models now? The official selection manual from 2019 has as many as 75 pages.
Students who need the 2019 STM32 selection manual can click this link to download:
https://mr-wu-cdn-bucket.oss-cn-shenzhen.aliyuncs.com/Selection%20Guide%2020190329.pdf
At the same time, ST has provided an online product selector on its official website to help you conveniently choose the right STM32 products, and has developed the ST MCU Finder, which is available on both mobile and PC platforms. The PC version is cross-platform and can be used on desktop systems like MacOS, Windows, and Linux, making it easy for you to select their processors anytime, anywhere. Their market success is not without reason.
I personally prefer using the desktop version of the ST MCU Finder, as it is much more intuitive than the mobile app, especially with a larger screen.
The PC program can be downloaded and installed through the link below:
https://www.st.com/content/st_com/en/products/development-tools/software-development-tools/stm32-software-development-tools/stm32-utilities/st-mcu-finder-pc.html
The application data can be updated online, eliminating the need to refer to PDF or Excel selection manuals. Of course, ST’s website also has a web-based product selection tool, which is also quite good. If I remember correctly, the web-based product selector was initially developed based on Adobe’s Flex, requiring the Flash plugin to display in the browser. Now it has transitioned to HTML5, providing a better experience. The latest selection data for the chips is stored in the cloud, so there is no need for online updates. Every time you open the webpage, you get the latest data without needing to install anything on your computer, which is a plus. The only downside is that the web version lacks the price filtering option available in the PC version, which allows filtering and sorting based on unit price and shows the corresponding reference development board for the chips. That’s why I installed the PC product selector.
For example, if you want to select an STM32 MCU with USB Device functionality, you can check the USB Device option under peripheral features, and choose LQFP32 for the package based on the number of IO requirements. After filtering by these two criteria, you can narrow down the IC selection range to a manageable level.
The remaining considerations are Flash capacity, temperature range, price, distributor inventory, and lead time. For the same package with consistent peripheral specifications, different ICs can be Pin2Pin compatible.
For instance, after preliminary filtering, for the same LQFP32 package with USB Device functionality, we have identified STM32F series, STM32L series, and STM32G series.
Then, sorting by the procurement price per 10K, we find that the STM32F042K4 has the lowest unit price at $1.013 for 10K units, though the actual price depends on domestic distributor conditions.
Let’s see how ST officially categorizes and names the STM32F, STM32L, and STM32G series.
STM32 refers to the 32-bit MCU family, while there is also an 8-bit MCU family called STM8. Recently, ST introduced the STM32MP1, which is based on Cortex-A MPU, and is categorized under the [Microcontrollers] section on their website, with a separate [STM32MP1 Series] line for general-purpose microprocessors. It’s a bit confusing.
I personally think that this new MPU product line may be trying to leverage the popularity of the STM32 to boost the MPU’s visibility, and since the STM32MP1 integrates a Cortex-M4, it doesn’t hurt to ride on that wave. Once the Cortex-A MPU product line is more developed, they can separate it out later.
Currently, the STM32 product line categorizes the MP1 separately. The MP1 is a 32-bit microprocessor (MPU) based on the Cortex-A and Cortex-M cores, while the others are based on the Cortex-M core and are 32-bit microcontrollers (MCU).
Next, we categorize the 32-bit microcontrollers (MCUs) based on the Cortex-M core into:
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Mainstream product line
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Wireless product line
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Ultra-low power product line
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High-performance product line
Let’s take a look at the specific naming breakdown for the STM32F042K4.
STM32F0: Mainstream product line
42: Specific sub-product line
K: Package 32pin
4: On-chip Flash capacity 16K Bytes
With this breakdown, the functional specifications of this IC are established. However, for supply chain BOM purposes, this level of detail is still insufficient. We should specify something like STM32F042K4T6 to constrain it to the LQFP32 package and a temperature range of -40~85℃.
Different temperature ranges can lead to different procurement costs, and while different suffix ICs may serve the same function for R&D, variations in temperature ratings, ESD protection levels, etc., can result in differing procurement costs. Nowadays, mainstream EDA software has comprehensive BOM and schematic data management capabilities, which should be utilized to avoid issues with the supply chain.