I am doing a project for NFC EV charger billing system. I want to write a program that when ISO 14443A card placed near the PN532 NFC shield. Two 7-segments display will act a countdown timer to count from 20 to 00. When the time reaches to 00 and I placed the ISO 14443A card near the NFC shield again. Two 7-segment displays did not count down. What can I do for this program to make the countdown goes again when ISO 14443A placed near the NFC shield?
sketch_feb16b.ino (16.6 KB)