Audrino Uno EEPROM question

Projects General Guidance
1

Hi,

I am using an Audrino Uno with a fingerprint sensor and a TFT display. I have a ID counter which runs every time I run the code and the user tries to enroll a fingerprint, so this data is stored in that specific ID. For example: at the start the ID value is 1 and the first user who enrolls gets the data stored in ID1 and this goes on.
The issue I have is when I turn off the audrino or reset it, the ID value reinitiates again from 1 and erases the last fingerprint which was stored in ID=1 and stores the new fingerprint.
In order to resolve that I was thinking on using the EEPROM. I was thinking of using an counter with EEPROM address as 1 and ID as 1, so the counter keeps incrementing and storing the data in respective addresses. So I am back to the old issue where how would I continue from the last stored Address after power cycle/reset?
Can someone point out to an example?

2

Retrieve the value saved by EEPROM.put() by using EEPROM.get() in setup().

Look at the EEPROM library examples in the IDE, too.

A tutorial.

1 Like
3

Thanks a ton for the idea.
I was able to use that and coupled it with another logic where I could wrote sentinel value to the EEPROM locations initially say 255. Then as I handled the fingerprints I replaced that 255 with other values. When the code started, it would just scan through EEPROM looking for the first location containing 255, and that's the next one to use.

4

Or, preferably, EEPROM.update() to prevent unnecessary rewrites of identical values causing unnecessary wear of the EEPROM.

5

The EEPROM.put() reference says:

This function uses EEPROM.update() to perform the write, so does not rewrites the value if it didn't change.

6

Ah, I confused put and write. My bad!

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