Programming Cortex-M23 microcontrollers in bare metal mode using uVision5 can be challenging for beginners. Here are some tips to help you get started and be productive with this powerful toolchain.
1. Understand the Cortex-M23 architecture
The Cortex-M23 is one of Arm’s microcontroller cores designed for deeply embedded applications. It has a 3-stage pipeline, supports the Armv8-M architecture, and includes features like fault exceptions, interrupts, sleep modes, bit-banding, and more. Familiarize yourself with the reference manual to leverage these capabilities effectively.
2. Configure your project build settings
After creating a new uVision5 project, go to Project > Options for Target to configure important settings like the CPU core, instruction set, endian mode, runtime library, and code generation options. For bare metal projects, start with a Release build for optimum performance.
3. Set up CMSIS headers and startup code
Add the CMSIS headers for your MCU and the appropriate startup code to initialize the stack pointer, interrupts, etc. Arm provides CMSIS packs that can be easily imported into your project. Configure the include paths to locate them.
4. Write your C application code
With the project environment set up, you can start coding your C/C++ application logic. Make use of Arm CMSIS APIs to configure peripherals, enable interrupts, manage power modes, and more. Structure your code into logical files and functions.
5. Handle interrupts and exceptions
The Cortex-M23 allows handling exceptions like resets, faults, and interrupts via vector table entries. Write separate handler functions for each entry and add logic to service the event. Use CMSIS APIs to enable the appropriate interrupts.
6. Configure Project > Debugger settings
To debug your code, the debugger mode must match the target device interface – JTAG, SWD, etc. Configure debug access port, flash programming, and other settings correctly for your hardware. Test out basic stepping and breakpoints.
7. Build, flash and debug your code
After coding, build your project for the target MCU. Use the Flash options to program the executable to device flash. Then start a debug session, set breakpoints, inspect variables, and step through code execution. Fix bugs as they are uncovered.
8. Optimize critical code paths
Profile your application to identify performance bottlenecks. Use compiler optimizations, reduce function calls, tweak loop counters, unpack structures, utilize bit-banding, and hand-optimize assembly for frequently executed code paths.
9. Measure code size and memory usage
Deeply embedded apps require smaller code size and tight memory constraints. Use linker configurations to generate .map files. These provide detailed insight into code/data size per function, stack usage, heap allocation, etc.
10. Leverage MPU for memory protection
The MPU allows creating protected memory regions to isolate and guard critical code and data. Use MPU regions to prevent stack/heap overflows, restrict access to peripherals, and strengthen security.
11. Use SEGGER tools to analyze performance
SEGGER tools like SystemView, J-Link, and Ozone integrate tightly with uVision5. SystemView gives real-time execution traces to optimize task interaction. Ozone steps through source code for quick debugging.
12. Build tests for functionality and stress testing
Rigorously test your Cortex-M23 application under different conditions such as varying clocks, voltages, interrupts, data inputs, requests, etc. Unit tests modularize functionality checking. Automated tests enable regression testing.
13. Write firmware following a modular architecture
Craft the firmware following layers separating hardware abstraction, drivers, networking stack, middleware, the OS, application logic etc. This modularity aids testing and maintenance after product release.
14. Use fixed-point math libraries
The Cortex-M23 works best with integer and fixed-point math. Leverage fixed-point math libraries for transforms, matrix operations, filtering, PID control etc. Save FP for selective complex algorithms.
15. Build a hardware abstraction layer
Firmware re-use across projects requires isolating hardware dependencies. Constructing an HAL with standardized APIs abstracts the underlying MCU allowing portability across Cortex-M variants.
16. Enable and configure the Memory Protection Unit
Use the MPU to protect critical firmware assets like the vector table, bootloader, OS kernel etc. from corruption. MPU regions strengthened firmware resilience and security.
17. Use uVision5 to import existing code projects
uVision5 allows importing code projects created in other tools like CubeIDE/SW4STM32. Simply point to the right folders and it will automatically detect sources, include paths, libraries etc. Very handy when migrating projects over to uVision5.
18. Speed up builds with precompiled headers
Precompiled headers avoid recompiling unchanged header files every build. Just rebuild parts that changed. Make use of precompiled headers to slash build times on larger projects.
19. Design error handling with assertions and logs
Plan robust error handling with assertions to catch bugs early. Log error conditions verbosely to module-specific log files. Debugging is vastly simplified when errors are designed-in from the start.
20. Utilize CMSIS-RTOS2 for task scheduling
For complex concurrent applications, integrate a real-time OS like CMSIS-RTOS2 to schedule tasks. Use its APIs for mutexes, semaphores, message queues etc. CMSIS integration results in a tight footprint.
By following these tips while building your embedded applications on the Cortex-M23 using uVision5, you can boost your productivity and write high-quality production-grade firmware. Mastering the toolchain and MCU architecture enables you to exploit the full capabilities on offer. By applying robust firmware design principles, you can architect reliable and secure products. Consistent testing is key to ensuring correctness. uVision5, alongside complementary tools like the Arm compiler, debugger, and analyzer facilitate an efficient development workflow critical for success.
