使用 Zephyr RTOS 在 arm 嵌入式系统上处理日期和时间（struct tm）

Question

我正在尝试在我的 arm 微处理器板上获取当前日期时间并执行一些简单的数学运算（从 GMT 更改为 EST，然后转换为日历时间）。

我已经能够通过 AT 命令获得准确的网络 GMT 时间。它以以下格式返回：“20/01/02,16:31:07-20”。我已经解析了这个 char 数组并将相关值分配给 tm struct。我可以很好地打印单个值，但是当我尝试使用strftime 打印时，应用程序就会停止。一旦我开始工作，我将如何将其转换为日历时间（从纪元开始的秒数）我认为mktime 应该可以解决问题，但我认为同样的原因也会失败。任何人都有任何想法。这是代码和输出

    char datetime[] = "20/01/02,16:31:07-20";
    //just hardcoded for now to get formatting and math done properly
    char sep[] = " ,.-:/";
    char str[30];
    strcpy(str,datetime);
    struct tm *timekeeper;
    char* token = strtok (str, sep);
    int tempyear = atoi(token);
    if(tempyear < 100){
          timekeeper->tm_year = 2000 + tempyear;
          printk("year= %i\n",timekeeper->tm_year);
    }
    else{
          timekeeper->tm_year = tempyear;
    }
    token = strtok(NULL, sep);
    //months are set from 0 to 11 so -1 is needed to adjust
    timekeeper->tm_mon = atoi(token) - 1;
    printk("tm_mon= %i\n",timekeeper->tm_mon);
    token = strtok(NULL, sep);
    timekeeper->tm_mday = atoi(token);
    printk("tm_day= %i\n",timekeeper->tm_mday);
    token = strtok(NULL, sep);
    timekeeper->tm_hour = atoi(token);
    printk("tm_hour= %i\n",timekeeper->tm_hour);
    token = strtok(NULL, sep);
    timekeeper->tm_min = atoi(token);
    printk("tm_min= %i\n",timekeeper->tm_min);
    token = strtok(NULL, sep);
    timekeeper->tm_sec = atoi(token);
    timekeeper->tm_isdst = 0;
    printk("tm_sec= %i\n",timekeeper->tm_sec);
    char buffer[40];
    //strftime(buffer, 26, "%Y-%m-%d %H:%M:%S", timekeeper);
    //int secondsfromepoch = mktime(timekeeper);
    strftime(buffer, 40, "%A", timekeeper);
    printk("test\n");
    printk("date and time= %s\n",buffer);

尝试了新代码：

     timekeeper->tm_year = 120; 
     timekeeper->tm_mon = 1; 
     timekeeper->tm_mday = 1; 
     timekeeper->tm_hour = 10; 
     timekeeper->tm_min = 10; 
     timekeeper->tm_sec = 10; 
     timekeeper->tm_isdst = 0; 
     char buffer[40]; 
     printk("year= %i\n",timekeeper->tm_year); 
     printk("tm_mon= %i\n",timekeeper->tm_mon); 
     printk("tm_day= %i\n",timekeeper->tm_mday); 
     printk("tm_hour= %i\n",timekeeper->tm_hour); 
     printk("tm_min= %i\n",timekeeper->tm_min); 
     printk("tm_sec= %i\n",timekeeper->tm_sec);

输出：

year= 2020
tm_mon= 0
tm_day= 2
tm_hour= 16
tm_min= 31
tm_sec= 7

新代码尝试输出：

year= 120 
tm_mon= 1 
tm_day= 1 
tm_hour= 10 
tm_min= 10 
tm_sec= 10 

Answer 1

struct tm 的 year 字段需要 year - 1900 的值。

所以在你的情况下，它应该包含值120，而不是2020。

另外，指针timekeeper 永远不会被设置。因此，当您尝试通过 -> 运算符取消引用该未初始化指针时，您调用了 undefined behavior。

将timekeeper 更改为struct tm 的实例而不是指针：

struct tm timekeeper;

并将其上的 -> 运算符的任何实例调整为 .。

Answer 2

struct tm 纪元年是 1900 年而不是零：

    if(tempyear < 100)
    {
          timekeeper->tm_year = 100 + tempyear;
    }
    else
    {
          timekeeper->tm_year = tempyear - 1900;
    }

    printk( "year= %i\n", timekeeper->tm_year + 1900 ) ;

或者，因为它是您可能更喜欢的简单条件赋值：

timekeeper->tm_year = (tempyear < 100) ? 100 + tempyear : 
                                         tempyear - 1900 ;
printk( "year= %i\n", timekeeper->tm_year + 1900 ) ;