如何在4个字节内保存日期时间戳 [英] How to save date time stamp within 4 bytes

问题描述

我想将嵌入式系统的开始时间和日期记录到内存中。
在这里我想知道有什么标准可以在4个字节内保存日期时间戳。

该系统在具有免费rtos的arm7上工作。董事会包含RTC

谢谢。

I want to log my embedded system start time and date in to memory. here I want to know that there is any standard to save datetime stamp within 4 bytes.
The system is worked on arm7 with free rtos. The board contains RTC
Thanks.

推荐答案

以下结构显示了三种存储时间和日期的方法在4个字节（或32位）之内。

The structures below show three methods of storing time and date within 4 bytes (or 32 bits).

#pragma pack(1)
typedef struct TIMESTAMP_32_A_S
   {
   uint8_t   seconds    : 6; // 0-60 (0-63 max)
   uint8_t   minutes    : 6; // 0-60 (0-63 max)
   uint8_t   hours24    : 5; // 0-23 (0-31 max)
   uint8_t   dayOfMonth : 5; // 1-31 (0-31 max)
   uint8_t   month      : 4; // 1-12 (0-15 max)
   uint8_t   year       : 6; // Epoch start: 2014, Range: 2014 thru 2077
   } TIMESTAMP_32_A_T;                                                  
#pragma pack()

以上结构假定<$ c $的粒度c> seconds 对应用程序很重要。它还假设在 year 2014之前或 year 2077之后不会执行该应用程序（此时时间，年会追溯到2014年。）

The structure above assumes that the granularity of seconds is important to the application. It also assumes that the application will not be executed prior to the year 2014, or after the year 2077 (at which time, year will roll back to 2014).

#pragma pack(1)
typedef struct TIMESTAMP_32_B_S
   {
   uint8_t   minutes    : 6; // 0-60 (0-63 max)
   uint8_t   hours24    : 5; // 0-23 (0-31 max)
   uint8_t   dayOfMonth : 5; // 1-31 (0-31 max)
   uint8_t   month      : 4; // 1-12 (0-15 max)
   uint16_t  year       : 12; // Epoch start: 2014, Range: 2014 thru 4061
   } TIMESTAMP_32_B_T;
#pragma pack()

以上结构假定秒与该应用程序无关。它还假定在 year 2014之前或 year 4061之后不会执行该应用程序（此时时间，年将回溯到2014年）。

The structure above assumes that seconds are irrelevant to the application. It also assumes that the application will not be executed prior to the year 2014, or after the year 4061 (at which time, year will roll back to 2014).

#pragma pack(1)
typedef struct TIMESTAMP_32_C_S
   {
   uint8_t   secondsBy2 : 5; // 0-30 (0-31 max)
   uint8_t   minutes    : 6; // 0-60 (0-63 max)
   uint8_t   hours24    : 5; // 0-23 (0-31 max)
   uint8_t   dayOfMonth : 5; // 1-31 (0-31 max)
   uint8_t   month      : 4; // 1-12 (0-15 max)
   uint8_t   year       : 7; // Epoch start: 2014, Range: 2014 thru 2141
   } TIMESTAMP_32_C_T;
#pragma pack()

以上结构假定 2秒间隔的秒数足以满足应用程序的需要。它还假定在 year 2014之前或 year 2141之后不会执行该应用程序。时间，年将回溯到2014年）。 MSDOS使用了类似的结构。

The structure above assumes that a seconds granularity of 2-second intervals are is sufficient to the application. It also assumes that the application will not be executed prior to the year 2014, or after the year 2141 (at which time, year will roll back to 2014). MSDOS used a similar structure.

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