i have car park project with arduino mega. i use 2 rfids. First RFID (mfrc522) controls entry barrier. second RFID contols exit barier. i use an rfid-controlled servo motors. i can get time on serial with rtc(ds3231).
But i need to taking time difference.
for example car is entry time 21:31:37. and this car exit time 21:33:42. i need to taking time difference on minute. the car was inside for 2 minutes. I have to charge you accordingly. how can i get this time. help me pls