72 lines
1.8 KiB
C++
72 lines
1.8 KiB
C++
/***
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EEPROM Update method
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Stores values read from analog input 0 into the EEPROM.
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These values will stay in the EEPROM when the board is
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turned off and may be retrieved later by another sketch.
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If a value has not changed in the EEPROM, it is not overwritten
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which would reduce the life span of the EEPROM unnecessarily.
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Released using MIT licence.
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***/
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#include <EEPROM.h>
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/** the current address in the EEPROM (i.e. which byte we're going to write to next) **/
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int address = 0;
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void setup() {
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/** EMpty setup **/
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}
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void loop() {
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/***
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need to divide by 4 because analog inputs range from
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0 to 1023 and each byte of the EEPROM can only hold a
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value from 0 to 255.
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***/
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int val = analogRead(0) / 4;
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/***
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Update the particular EEPROM cell.
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these values will remain there when the board is
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turned off.
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***/
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EEPROM.update(address, val);
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/***
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The function EEPROM.update(address, val) is equivalent to the following:
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if( EEPROM.read(address) != val ){
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EEPROM.write(address, val);
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}
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***/
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/***
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Advance to the next address, when at the end restart at the beginning.
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Larger AVR processors have larger EEPROM sizes, E.g:
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- Arduno Duemilanove: 512b EEPROM storage.
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- Arduino Uno: 1kb EEPROM storage.
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- Arduino Mega: 4kb EEPROM storage.
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Rather than hard-coding the length, you should use the pre-provided length function.
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This will make your code portable to all AVR processors.
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***/
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address = address + 1;
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if (address == EEPROM.length()) {
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address = 0;
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}
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/***
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As the EEPROM sizes are powers of two, wrapping (preventing overflow) of an
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EEPROM address is also doable by a bitwise and of the length - 1.
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++address &= EEPROM.length() - 1;
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***/
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delay(100);
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}
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