How does C++ interact with underlying hardware in embedded development?

In embedded development, C++ interacts with the underlying hardware through: Pointer and address addressing: direct access to hardware registers and memory locations. Memory mapped I/O: Map hardware registers into memory address space and use standard C++ code to manipulate the registers. Interrupt handling: Respond to hardware interrupt events in a timely manner. Through these interactions, C++ can efficiently control and operate embedded systems, such as setting GPIO pins, sending serial port data, and controlling timers.

C++ interacts with the underlying hardware in embedded development

In embedded development, C++ is widely used because of its efficient and low-level features . By interacting directly with the underlying hardware, C++ can efficiently control and operate embedded systems. This article will explore the mechanism of C++ interacting with underlying hardware in embedded development and illustrate it through practical cases.

1. Pointer and address addressing

C++ uses pointers and addresses to directly access the underlying hardware. Pointers point to specific memory addresses, while address addressing allows direct modification of hardware registers and memory locations. This enables C++ to operate low-level hardware components such as GPIO pins, UART interfaces, and timers.

Code sample:

// 定义 GPIO 引脚的指针
uint8_t *gpio_ptr = (uint8_t *)0x12345678;

// 设置 GPIO 引脚为高电平
*gpio_ptr |= 0x01 << 3;

2. Memory mapped I/O

Memory mapped I/O is a kind of Technology that maps hardware registers to memory address space. This allows standard C++ code to access and manipulate hardware registers as if they were ordinary memory locations.

Code example:

// 定义 UART 寄存器的内存映射地址
uint32_t *uart_base_addr = (uint32_t *)0x12345678;

// 发送字符到串口
uart_base_addr[0] = 'a';

3. Interrupt processing

Interrupt is an event that triggers the CPU to suspend the current Perform the task and handle the event. C++ provides an interrupt handling mechanism that allows programs to respond to hardware interrupts in a timely manner.

Code example:

// 定义中断服务例程
void interrupt_handler() {
  // 处理中断事件
}

// 注册中断服务例程
IRQ_RegisterInterruptHandler(interrupt_handler);

Practical case: controlling LED light flashing

Requirements:

• Microcontroller: STM32F103C8T6
• LED connected to GPIOA.5 pin

##Steps:

Use the pointer to set the GPIOA.5 pin to output mode.
Use memory mapped I/O to operate the GPIOA.5 register to toggle the state of the LED.
Use an interrupt timer to trigger LED flashes periodically.

Code example:

#include <stm32f10x.h>

int main() {
  // 设置 GPIOA.5 引脚为输出模式
  GPIOA->CRL &= ~(GPIO_CRL_CNF5_0 | GPIO_CRL_CNF5_1);
  GPIOA->CRL |= GPIO_CRL_CNF5_1;

  // 使用内存映射 I/O 操作 GPIOA.5 寄存器
  GPIOA->ODR |= GPIO_ODR_ODR5;  // 打开 LED

  // 使用中断定时器定期触发 LED 闪烁
  TIM2->CR1 = TIM_CR1_CEN;  // 启动定时器
  TIM2->ARR = 500;  // 设置闪烁周期为 500 毫秒
  TIM2->DIER |= TIM_DIER_UIE;  // 启用更新中断

  // 进入无限循环以保持程序运行
  while (1) {}
}

// 中断服务例程
void TIM2_IRQHandler() {
  // 处理中断事件（切换 LED 状态）
  GPIOA->ODR ^= GPIO_ODR_ODR5;

  // 清除中断标志位
  TIM2->SR &= ~TIM_SR_UIF;
}

Conclusion:

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