CMSIS-CORE
Version 3.01
CMSIS-CORE support for Cortex-M processor-based devices
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To use the CMSIS-CORE the following files are added to the embedded application:
The Startup File startup_<device>.s is executed after reset and calls SystemInit. After the system initialization control is transferred to the C/C++ run-time library which performs initialization and calls the main function in the user code. In addition the Startup File startup_<device>.s contains all exception and interrupt vectors and implements a default function for every interrupt. It may also contain stack and heap configurations for the user application.
The System Configuration Files system_<device>.c and system_<device>.h performs the setup for the processor clock. The variable SystemCoreClock indicates the CPU clock speed. System and Clock Configuration describes the minimum feature set. In addition the file may contain functions for the memory BUS setup and clock re-configuration.
The Device Header File <device.h> is the central include file that the application programmer is using in the C source code. It provides the following features:
The CMSIS-CORE are device specific. In addition, the Startup File startup_<device>.s is also compiler vendor specific. The various compiler vendor tool chains may provide folders that contain the CMSIS files for each supported device. Using CMSIS with generic ARM Processors explains how to use CMSIS-CORE for ARM processors.
For example, the following files are provided in MDK-ARM to support the STM32F10x Connectivity Line device variants:
File | Description |
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".\ARM\Startup\ST\STM32F10x\startup_stm32f10x_cl.s" | Startup File startup_<device>.s for the STM32F10x Connectivity Line device variants. |
".\ARM\Startup\ST\STM32F10x\system_stmf10x.c" | System Configuration Files system_<device>.c and system_<device>.h for the STM32F10x device families. |
".\ARM\INC\ST\STM32F10x\stm32f10x.h" | Device Header File <device.h> for the STM32F10x device families. |
".\ARM\INC\ST\STM32F10x\system_stm32f10x.h" | system_Device.h Template File for the STM32F10x device families. |
Thereafter, the functions described under Reference can be used in the application.
A typical example for using the CMSIS layer is provided below. The example is based on a STM32F10x Device.
#include <stm32f10x.h> // File name depends on device used uint32_t volatile msTicks; // Counter for millisecond Interval void SysTick_Handler (void) { // SysTick Interrupt Handler msTicks++; // Increment Counter } void WaitForTick (void) { uint32_t curTicks; curTicks = msTicks; // Save Current SysTick Value while (msTicks == curTicks) { // Wait for next SysTick Interrupt __WFE (); // Power-Down until next Event/Interrupt } } void TIM1_UP_IRQHandler (void) { // Timer Interrupt Handler ; // Add user code here } void timer1_init(int frequency) { // Set up Timer (device specific) NVIC_SetPriority (TIM1_UP_IRQn, 1); // Set Timer priority NVIC_EnableIRQ (TIM1_UP_IRQn); // Enable Timer Interrupt } void Device_Initialization (void) { // Configure & Initialize MCU if (SysTick_Config (SystemCoreClock / 1000)) { // SysTick 1mSec : // Handle Error } timer1_init (); // setup device-specific timer } // The processor clock is initialized by CMSIS startup + system file void main (void) { // user application starts here Device_Initialization (); // Configure & Initialize MCU while (1) { // Endless Loop (the Super-Loop) __disable_irq (); // Disable all interrupts Get_InputValues (); // Read Values __enable_irq (); // Enable all interrupts Calculation_Response (); // Calculate Results Output_Response (); // Output Results WaitForTick (); // Synchronize to SysTick Timer } }