ARM Cortex-M Skill

Overview

This skill provides deep expertise in ARM Cortex-M architecture, including core configuration, peripheral programming, and low-level optimization for the most widely used embedded processor family.

Capabilities

CMSIS Integration

• CMSIS-Core configuration and usage
• CMSIS-Driver integration
• CMSIS-DSP library utilization
• CMSIS-RTOS abstraction
• Device header file management

NVIC Configuration

• Interrupt priority configuration
• Priority grouping setup
• Vector table relocation
• Interrupt enable/disable patterns
• Nested interrupt handling

Memory Protection Unit (MPU)

• MPU region setup and configuration
• Memory attribute configuration
• Protection scheme design
• Stack overflow protection
• Peripheral isolation

System Timers

• SysTick timer configuration
• DWT cycle counter usage
• Timer-based profiling
• Timestamp generation
• Delay implementations

Fault Handling

• HardFault analysis and debugging
• BusFault configuration
• UsageFault detection
• MemManage fault handling
• Fault register interpretation

Low-Level Optimization

• ARM assembly for critical sections
• Bit-banding operations
• Atomic operations (LDREX/STREX)
• Barrier instructions (DSB, DMB, ISB)
• Compiler intrinsics

Power Management

• WFI/WFE instruction usage
• Sleep mode entry/exit
• Wake-up source configuration
• Low-power mode selection
• Power domain management

Target Processes

• bsp-development.js - BSP with Cortex-M support
• isr-design.js - Interrupt architecture design
• memory-architecture-planning.js - Memory layout with MPU
• real-time-architecture-design.js - Real-time Cortex-M design
• bootloader-implementation.js - Cortex-M bootloader

Dependencies

• ARM CMSIS headers
• Cortex-M technical reference manual
• Device-specific headers

Usage Context

This skill is invoked when tasks require:

• Cortex-M core configuration
• Interrupt system design
• MPU setup and protection
• Fault debugging and analysis
• Low-level performance optimization

Architecture Support

| Core | Features | |------|----------| | Cortex-M0/M0+ | Minimal, low-power | | Cortex-M3 | Full Thumb-2, MPU optional | | Cortex-M4 | DSP, optional FPU | | Cortex-M7 | Cache, dual-issue | | Cortex-M23 | TrustZone-M, security | | Cortex-M33 | TrustZone-M, DSP | | Cortex-M55 | MVE (Helium), ML |

Example Configurations

NVIC Priority

c
NVIC_SetPriorityGrouping(3);  // 4 bits preemption, 0 bits sub
NVIC_SetPriority(USART1_IRQn, NVIC_EncodePriority(3, 2, 0));
NVIC_EnableIRQ(USART1_IRQn);

MPU Region

c
MPU->RNR = 0;  // Region 0
MPU->RBAR = 0x20000000;  // Base address
MPU->RASR = MPU_RASR_ENABLE_Msk |
            (0x0F << MPU_RASR_SIZE_Pos) |  // 64KB
            MPU_RASR_C_Msk | MPU_RASR_S_Msk;