課程: Udemy-Embedded-Systems-Bare-Metal-Programming
板子: NUCLEO-F446RE
起始花費: NT$850(板子) + NT$370(Udemy)
文件:
Source Code:
1. Getting Started - Constructing Peripheral Registers from Memory Addresses
| 縮寫 | |
|---|---|
| APB | Advanced Peripheral Bus |
| AHP | Advanced High-performance Bus |
| RCC | Reset and Clock Control |
| ODR | Output Data Register 輸出資料暫存器 |
ex1: 讓LED持續亮
ex2: 讓LED閃爍
/* Peripheral base address */
#define PERIPH_BASE (0x40000000UL)
/* AHB1 and AHB2 offsets */
#define AHB1_OFFSET (0x00020000UL)
#define AHB2_OFFSET (0x10000000UL)
/* AHB base addresses */
#define AHB1_PERIPH_BASE (PERIPH_BASE + AHB1_OFFSET)
#define AHB2_PERIPH_BASE (PERIPH_BASE + AHB2_OFFSET)
/* RCC */
#define RCC_OFFSET (0x00003800UL)
#define RCC_BASE (AHB1_PERIPH_BASE + RCC_OFFSET)
/* GPIOA */
#define GPIOA_OFFSET (0x00000000UL)
#define GPIOA_BASE (AHB1_PERIPH_BASE + GPIOA_OFFSET)
/* RCC AHB1 clock enable register */
#define AHB1EN_R_OFFSET (0x30UL)
#define RCC_AHB1EN_R (*(volatile unsigned int *)(RCC_BASE + AHB1EN_R_OFFSET))
/* GPIOA mode register */
#define MODE_R_OFFSET (0x00UL)
#define GPIOA_MODE_R (*(volatile unsigned int *)(GPIOA_BASE + MODE_R_OFFSET))
/* GPIOA output data register */
#define OD_R_OFFSET (0x14UL)
#define GPIOA_OD_R (*(volatile unsigned int *)(GPIOA_BASE + OD_R_OFFSET))
/* Pin definitions */
#define PIN_5 (1U << 5)
#define LED_PIN PIN_5
/* GPIOA clock enable */
#define GPIOAEN (1U << 0)
int main(void)
{
/* 1. Enable GPIOA clock */
RCC_AHB1EN_R |= GPIOAEN;
/* 2. Clear PA5 mode bits */
GPIOA_MODE_R &= ~(3U << 10);
/* 3. Set PA5 as output (01) */
GPIOA_MODE_R |= (1U << 10);
/* 4. Turn on LED */
GPIOA_OD_R |= LED_PIN;
while (1)
{
/* 5. Toggle LED */
GPIOA_OD_R ^=LED_PIN;
for(int i=0;i<100000;i++){}
}
}
STM32 使用 Memory-Mapped I/O（記憶體映射輸入輸出）。
MCU 把 GPIO、RCC、USART、Timer 等硬體周邊的暫存器，映射到固定的記憶體位址
Mode Register（MODER）用來設定 GPIO 腳位的模式
透過struct簡化程式碼
#include <stdint.h>
#define PERIPH_BASE (0x40000000UL)
#define AHB1PERIPH_OFFSET (0x00020000UL)
#define AHB1PERIPH_BASE (PERIPH_BASE + AHB1PERIPH_OFFSET)
#define GPIOA_OFFSET (0x00000000UL)
#define GPIOA_BASE (AHB1PERIPH_BASE + GPIOA_OFFSET)
#define RCC_OFFSET (0x00003800UL)
#define RCC_BASE (AHB1PERIPH_BASE + RCC_OFFSET)
#define PIN5 (1U << 5)
#define LED_PIN PIN5
/* GPIOA clock enable */
#define GPIOAEN (1U << 0)
/* RCC register structure */
typedef struct
{
volatile uint32_t DUMMY[12];
volatile uint32_t AHB1ENR;
} RCC_TypeDef;
/* GPIO register structure */
typedef struct
{
volatile uint32_t MODER;
volatile uint32_t DUMMY[4];
volatile uint32_t ODR;
} GPIO_TypeDef;
/* Peripheral pointer definitions */
#define RCC ((RCC_TypeDef *)RCC_BASE)
#define GPIOA ((GPIO_TypeDef *)GPIOA_BASE)
int main(void)
{
/* 1. Enable GPIOA clock */
RCC_AHB1EN_R |= GPIOAEN;
RCC->AHB1ENR |= GPIOAEN;
/* 2. Set PA5 as output */
GPIOA_MODE_R &= ~(3U << 10);
GPIOA_MODE_R |= (1U << 10);
GPIOA->MODER |= (1U << 10);
GPIOA->MODER &= ~(1U << 11);
while (1){
/* Toggle PA5 */
GPIOA->ODR ^= LED_PIN;
for (int i = 0; i < 100000; i++){}
}
}