Permanent Data Storage with AVR Internal EEPROM.
EEPROM stands for Electrically Erasable Programmable Read-Only Memory. We can erase the EEPROM data by the UV eraser. The FLASH memory is faster than EEPROM. In flash memory, we have to erase the whole sector at a time but in the case of EEPROM, we can erase a single byte at the time. A good example to use EEPROM is a digital lock system.
EEPROM.write( address, value ) The write() method allows you to write a single byte of data to the EEPROM. Two parameters are needed. The first is an int containing the address that is to be written, and the second is a the data to be written (unsigned char). This function does not return any value. EEPROM.update( address, value ).
EEPROM Write: Stores values from an analog input to the EEPROM. EEPROM Crc: Calculates the CRC of EEPROM contents as if it was an array. EEPROM Get: Get values from EEPROM and prints as float on serial. EEPROM Iteration: Understand how to go through the EEPROM memory locations. EEPROM Put: Put values in EEPROM using variable semantics.
Although there is an EEPROM Write sketch, using the update method is a better choice when writing data to the EEPROM. This is because this method reads the EEPROM value first, and then only updates it if it is different, in fact it’s simply a combination of both the Read and Write method.
If you write a block which happens to be null-terminated, then reading it back should be fine. I do that when I want to save a filename in EEPROM. Just declare a suitable length (allowing room for the null terminator) and write the entire block to EEPROM.
The purpose of this example is to show the EEPROM.update() method that writes data only if it is different from the previous content of the locations to be written. This solution may save execution time because every write operation takes 3.3 ms; the EEPROM has also a limit of 100,000 write cycles per single location, therefore avoiding rewriting the same value in any location will increase.
The microcontroller based voting machines made the process of voting and counting the voted lot easier than before. Previously the votes were marked in paper which are then stored safely in a box and inside a well secure room for days. The process of separating the votes and counting them manually may take a lot of days. But after finding the electronic voting machine the votes can be marked.