The chip price is the easiest number on the quote. The software that makes the chip useful — drivers, an RTOS, stacks and a bootloader — is where many AT32 projects silently overspend, because that cost lands in engineering time and in recurring licence or maintenance fees rather than on the BOM. This article separates the free parts from the parts that will cost you.
Parts discussed: AT32F403ARGT7, AT32F405CCT7 for USB-heavy designs, AT32F455VET7 for Ethernet, and AT32F415CBT7.
What the free SDK actually covers
The vendor peripheral library and example set sit on the standard CMSIS layer and are provided without charge. That removes the largest single software expense: writing register-level drivers from nothing. What it does not remove is the engineering to port your application, validate the clock tree and qualify the build. The SDK lowers the entry cost; it does not remove the qualification cost.
Where middleware starts to cost
The moment you need a file system, a TCP/IP or USB stack, a GUI library or a secure-boot framework, the cost question opens up.
| Need | Free path | What it still costs you |
|---|---|---|
| RTOS | FreeRTOS / RT-Thread | Integration, certification, maintenance |
| File system | Open-source FAT/ LittleFS | Wear handling, power-loss safety |
| TCP/IP or USB stack | Vendor or open-source stack | Integration and testing |
| GUI on a display | Open library or vendor demo | Performance tuning, memory |
| Secure boot | Vendor bits plus your policy | Key management discipline |
The licence fee is often the smallest part. Integration and the long-term maintenance are the recurring line items.
RTOS: free is the default, paid is the argument
Most teams start on a free RTOS because it costs nothing to begin and has a huge community. The cost shows up as your own effort to integrate, certify and maintain. A commercial RTOS can be cheaper overall when you need certified behaviour, long-term vendor support or a specific safety argument — you are buying the evidence, not just the code.
Protect the software asset across changes
Keep application logic above the peripheral layer and treat the vendor SDK as a replaceable base. When you move between AT32 members, or from another Cortex-M part, the driver swap stays contained. Teams that let application code reach into registers directly pay the porting cost twice: once in engineering, once in re-qualification. A clean layering is the cheapest insurance in the product's life.
For related parts see Microcontrollers and MCUs and the AT32F413RBT7.
Frequently asked questions
Is the AT32 SDK free, and what does that actually save me?
The vendor provides a peripheral library and examples built on the standard CMSIS layer at no charge, which removes the largest single software cost: writing and maintaining register-level drivers from scratch. What it does not remove is the engineering to port your application, validate the clock tree and qualify the build. Free SDK lowers the entry cost; it does not remove the qualification cost.
When does middleware become a real cost?
As soon as you need a file system, a TCP/IP or USB stack, a GUI library or a secure-boot framework. Some of these ship as open-source or vendor-supported components, others are commercial with per-seat or per-device licensing. The cost is not only the licence fee but the integration and the long-term maintenance, and a commercial stack you depend on is a recurring line item, not a one-off.
FreeRTOS or a commercial RTOS — which is cheaper in practice?
FreeRTOS and RT-Thread are widely used on the AT32 and cost nothing to start, which is why most teams begin there. The cost appears as your own effort to integrate, certify and maintain. A commercial RTOS can be cheaper overall when you need certified behaviour, long-term support or a specific safety argument, because you are buying the evidence rather than building it.
How do I protect software investment across an MCU change?
Keep the application logic above the peripheral layer, and treat the vendor SDK as a replaceable base. When you move between AT32 members, or from another Cortex-M part, the driver swap is contained. Teams that let application code reach into registers directly pay the porting cost twice — once in engineering, once in re-qualification.
What software cost should I budget before the first production unit?
Three buckets: the porting and clock-tree validation, the integration of any middleware you need, and the qualification of the final image including the bootloader and protection settings. None of these is the芯片 price, all of them scale with the product's life, and ignoring them is how a 'free SDK' turns into the most expensive part of the project.
About us & trademarks: JTDZ Tech (Shenzhen Jingteng Electronics Technology Co., Ltd.) is an independent distributor of electronic components. We are not an authorised distributor or representative of the manufacturers named in this article. Manufacturer and part names are used for indicative purposes only, to help identify the components discussed; all trademarks remain the property of their respective owners. Always verify specifications against the manufacturer's datasheet before design-in or purchase.
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