Hello.... I am a beginner.. I wanna to make finger print voting machine using arduino with i2c lcd for my thesis.. However, i need helps in code. I want to access one fingerprint id only for one time. if the same fingerprint id is scanned next time. I want to show "Already Voted" on LCD.. Please help in coding for it... Any helps.. I really need help. Deadline is very closed...
Use EEPROM: for ease, one byte per fingerprint, and for retaining info over power cycles.
Before the vote, set all bytes to 0.
When a fingerprint has voted, set the byte with the same index to 1.
So when scanning a fingerprint check the EEPROM value for that ID. If 0, allow to vote; if 1 show your "already voted" message.
I've deleted your other cross post @AungPhyoKhant.
Cross posting is against the rules of the forum. The reason is that duplicate posts can waste the time of the people trying to help. Someone might spend 15 minutes writing a detailed answer on this thread, without knowing that someone else already did the same in the other thread.
Repeated cross posting will result in a suspension from the forum.
In the future, please take some time to pick the forum section that best suits the topic of your question and then only post once to that forum section. This is basic forum etiquette, as explained in the sticky "How to use this forum - please read." post you will find at the top of every forum section. It contains a lot of other useful information. Please read it.
Thanks in advance for your cooperation.