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/***
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:
- Arduino Duemilanove: 512 B EEPROM storage.
- Arduino Uno: 1 kB EEPROM storage.
- Arduino Mega: 4 kB 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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