Key Moments from Getting Started to Giving Up Embedded Development

#include <reg51.h>
sbit LED = P1^0;
void main(){ LED = 0;
 while(1);}

#include "stm32f4xx.h"
/* Main function */
int main(void){
 /* Enable GPIOH clock, always enable its clock before using peripherals */
 RCC_AHB1ENR |= (1<<7);
 /* LED port initialization */
 /* GPIOH MODER10 clear */
 GPIOH_MODER &= ~( 0x03<< (2*10));
 /* PH10 MODER10 = 01b output mode */
 GPIOH_MODER |= (1<<2*10);
 /* GPIOH OTYPER10 clear */
 GPIOH_OTYPER &= ~(1<<1*10);
 /* PH10 OTYPER10 = 0b push-pull mode */
 GPIOH_OTYPER |= (0<<1*10);
 /* GPIOH OSPEEDR10 clear */
 GPIOH_OSPEEDR &= ~(0x03<<2*10);
 /* PH10 OSPEEDR10 = 0b speed 2MHz */
 GPIOH_OSPEEDR |= (0<<2*10);
 /* GPIOH PUPDR10 clear */
 GPIOH_PUPDR &= ~(0x03<<2*10);
 /* PH10 PUPDR10 = 01b pull-up mode */
 GPIOH_PUPDR |= (1<<2*10);
 /* Set BR10 of GPIOH BSRR register to 1 to output low level */
 GPIOH_BSRR |= (1<<16<<10);  // Light up
 while (1);}

#include "stm32f10x.h"
/* LED clock port and pin definitions */
#define LED_PORT       GPIOC   
#define LED_PIN       GPIO_Pin_0
#define LED_PORT_RCC            RCC_APB2Periph_GPIOC
void LED_Init(){
 GPIO_InitTypeDef GPIO_InitStructure;        // Define structure variable
 RCC_APB2PeriphClockCmd(LED_PORT_RCC, ENABLE);
 GPIO_InitStructure.GPIO_Pin = LED_PIN;                // Select the IO port you want to set
 GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;      // Set push-pull output mode
 GPIO_InitStructure.GPIO_Speed=GPIO_Speed_50MHz;       // Set transmission speed
 GPIO_Init(LED_PORT,&GPIO_InitStructure);              // Initialize GPIO 
 GPIO_SetBits(LED_PORT, LED_PIN);                       // Pull the LED port high, turn off LED}
int main(){
 LED_Init();  GPIO_ResetBits(LED_PORT,GPIO_Pin_0);// Light up
 while(1);}

#include <wiringPi.h>
int main(void){
 wiringPiSetup();
 pinMode (7, OUTPUT);
 digitalWrite(7, HIGH);
 while(1);}

#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/miscdevice.h>
#include <linux/ioctl.h>
#include <linux/gpio.h> 
#include <mach/regs-gpio.h>
#include "led.h" 
static int led_open(struct inode *inode, struct file *file){      s3c2410_gpio_cfgpin(S3C2410_GPB(5), S3C2410_GPIO_OUTPUT);    s3c2410_gpio_setpin(S3C2410_GPB(5), 1);       return 0;} 
static int led_ioctl(struct inode *inode, struct file *file, unsigned int cmd, unsigned long arg){      switch (cmd) {          case LED_ON:                s3c2410_gpio_setpin(S3C2410_GPB(5), 0);                return 0;          case LED_OFF:                s3c2410_gpio_setpin(S3C2410_GPB(5), 1);                return 0;          default:                return -EINVAL;          }} 
static struct file_operations led_fops = {      .owner = THIS_MODULE,      .open = led_open,      .ioctl = led_ioctl,}; 
static struct miscdevice led_misc = {      .minor = MISC_DYNAMIC_MINOR,      .name = "led",      .fops = &led_fops,}; 
static int led_init(void){      return misc_register(&led_misc);} 
static void led_exit(void){      misc_deregister(&led_misc);} 
MODULE_LICENSE("Dual BSD/GPL");
module_init(led_init);
module_exit(led_exit);

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <unistd.h>
#include <stdio.h>
#include "led.h" 
int main(void){            int fd;             fd = open("/dev/led", O_RDWR);             if (fd < 0) {                        printf("No such device!\n");                        return -1;            }             while (1) {                        ioctl(fd, LED_ON);                        sleep(1);                        ioctl(fd, LED_OFF);                        sleep(1);                }         close(fd);             return 0;}