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:

By leveraging pointers, memory mapped I/O and interrupts processing, C++ can efficiently interact with the underlying hardware in embedded development. This interaction enables programs to directly control and operate hardware components, thereby achieving the performance and functionality required by embedded systems.

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