Arduino库教程-EEPROM-EEPROM Update

EEPROM Update（EEPROM更新）

• 在Arduino和genuino板上的微控制器有512字节的EEPROM存储器：当开发板关闭时（就像一个小型硬盘驱动器）开始记忆（即是保存这些数值）。

• 这个例子的目的是示范仅在本地它和先前写入的内容不同时，用EEPROM.update()方法向EEPROM写入数据。这个解决方案可以节省执行时间，因为每一个写操作需要3.3毫秒；EEPROM也有每个单位置100.000的写周期的限制，因此避免在任何位置重写相同的值将增加EEPROM的整体寿命。

硬件要求

• Arduino 或者 Genuino 开发板

电路

这个例子的电路没有额外的连接

图由 Fritzing 软件绘制

原理图

图由 Fritzing 软件绘制

样例代码

/***
   EEPROM Update method

   Stores values read from analog input 0 into the EEPROM.
   These values will stay in the EEPROM when the board is
   turned off and may be retrieved later by another sketch.

   If a value has not changed in the EEPROM, it is not overwritten
   which would reduce the life span of the EEPROM unnecessarily.

   Released using MIT licence.
 ***/

#include <EEPROM.h>

/** the current address in the EEPROM (i.e. which byte we're going to write to next) **/
int address = 0;

void setup() {
  /** EMpty setup **/
}

void loop() {
  /***
    need to divide by 4 because analog inputs range from
    0 to 1023 and each byte of the EEPROM can only hold a
    value from 0 to 255.
  ***/
  int val = analogRead(0) / 4;

  /***
    Update the particular EEPROM cell.
    these values will remain there when the board is
    turned off.
  ***/
  EEPROM.update(address, val);

  /***
    The function EEPROM.update(address, val) is equivalent to the following:

    if( EEPROM.read(address) != val ){
      EEPROM.write(address, val);
    }
  ***/


  /***
    Advance to the next address, when at the end restart at the beginning.

    Larger AVR processors have larger EEPROM sizes, E.g:
    - Arduno Duemilanove: 512b EEPROM storage.
    - Arduino Uno:        1kb EEPROM storage.
    - Arduino Mega:       4kb EEPROM storage.

    Rather than hard-coding the length, you should use the pre-provided length function.
    This will make your code portable to all AVR processors.
  ***/
  address = address + 1;
  if (address == EEPROM.length()) {
    address = 0;
  }

  /***
    As the EEPROM sizes are powers of two, wrapping (preventing overflow) of an
    EEPROM address is also doable by a bitwise and of the length - 1.

    ++address &= EEPROM.length() - 1;
  ***/

  delay(100);
}

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更多

• EEPROM.update()
• EEPROM library reference
• EEPROM Clear: 清理EEPROM里面的数据。
• EEPROM Read: 读取EEPROM，并且发送它的值到电脑。
• EEPROM Write: 保存模拟输入引脚的值到EEPROM。
• EEPROM Crc: 将EEPROM内容里的CRC当作数组分析。
• EEPROM Get: 从EEPROM获得一个值，并作为float格式串行打印。
• EEPROM Iteration: 明白怎样到达EEPROM存储本地。
• EEPROM Put: 用变量来把一些数值放到EEPROM里。
• EEPROM Update: 保存从A0读取的数值到EEPROM里，仅在不同的时候写入，以延长EEPROM寿命。