智能盒子oj | 使用EEPROM断电也能保存数据

EEPROM (Electrically Erasable Programmable Read-Only Memory)，电可擦可编程只读存储器–一种掉电后数据不丢失的存储芯片。
简而言之就是你想断电后arduino还要保存一些参数，就使用EEPROM吧。
在各型号的arduino控制器上的AVR芯片均带有EEPROM，也有外接的EEPROM芯片，常见arduino控制器的EEPROM大小：
Arduino UNO、Arduino duemilanove-m328、Zduino m328均使用ATmega328芯片，EEPROM都为1K
Arduino duemilanove-m168的EEPROM为512bytes
Arduino 2560的EEPROM为4K

下面我们介绍arduino自带的EEPROM使用方法，arduino的库已经为我们准备好了EEPROM类库，我们要使用得先调用EEPROM.h，然后使用write和read方法，即可操作EEPROM。
另：下面的官方例子由于写成较早，所以讲EEPROM的大小都定为了512字节，实际使用中，大家可参照上面所说的EEPROM大小，自行更改。

1.写入
选择 File>Examples>EEPROM>eeprom_write

/*
 * EEPROM Write
 *
 * 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.
 */
 
#include <EEPROM.h>
 
// EEPROM 的当前地址,即你将要写入的地址,这里就是从0开始写
int addr = 0;
 
void setup()
{
}
 
void loop()
{
  //模拟值读出后是一个0-1024的值，但每字节的大小为0-255，所以这里将值除以4再存储到val
  int val = analogRead(0) / 4;
   
  // write the value to the appropriate byte of the EEPROM.
  // these values will remain there when the board is
  // turned off.
  EEPROM.write(addr, val);
   
  // advance to the next address.  there are 512 bytes in 
  // the EEPROM, so go back to 0 when we hit 512.
  addr = addr + 1;
  if (addr == 512)
    addr = 0;
   
  delay(100);
}

2.读取
选择 File>Examples>EEPROM>eeprom_read

/*
 * EEPROM Read
 *
 * Reads the value of each byte of the EEPROM and prints it 
 * to the computer.
 * This example code is in the public domain.
 */
 
#include <EEPROM.h>
 
// start reading from the first byte (address 0) of the EEPROM
int address = 0;
byte value;
 
void setup()
{
  // initialize serial and wait for port to open:
  Serial.begin(9600);
  while (!Serial) {
    ; // wait for serial port to connect. Needed for Leonardo only
  }
}
 
void loop()
{
  // read a byte from the current address of the EEPROM
  value = EEPROM.read(address);
   
  Serial.print(address);
  Serial.print("\t");
  Serial.print(value, DEC);
  Serial.println();
   
  // advance to the next address of the EEPROM
  address = address + 1;
   
  // there are only 512 bytes of EEPROM, from 0 to 511, so if we're
  // on address 512, wrap around to address 0
  if (address == 512)
    address = 0;
     
  delay(500);
}

3.清除
选择 File>Examples>EEPROM>eeprom_clear
清除EEPROM的内容，其实就是把EEPROM中每一个字节写入0，因为只用清一次零，所以整个程序都在setup部分完成。

/* * EEPROM Clear
 *
 * Sets all of the bytes of the EEPROM to 0.
 * This example code is in the public domain.
 
 */
#include <EEPROM.h>
 
void setup()
{
  // 让EEPROM的512字节内容全部清零
  for (int i = 0; i < 512; i++)
    EEPROM.write(i, 0);
     
  // 清零工作完成后，将L灯点亮，提示EEPROM清零完成
  digitalWrite(13, HIGH);
}
 
void loop()
{
}

使用共用体结构保存其他类型的数据到EEPROM：http://www.arduino.cn/thread-2684-1-1.html

使用EEPROM断电也能保存数据

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