Welcome to CuVoodoo,
the sorcery of copper.
you will see it is not a "smart" card
the washing program
then the price to pay
to make the payment
ISO/IEC 7816 part 3: transmission protocols
not part 3 at least. only part 1 (card size) and 2 (contact positions)
what protocol it uses
which supports more protocols
USB
bottom
it's an I²C card, not a smart card
I²C: Inter-Integrated Circuit
it's a bus protocol
high on idle
it's not an exception, since it's not for data
technique
drives it high
SDA edge while SCL is high
the slave can keep the clock low until the data line is set (optional clock stretching)
and other special cases
start condition. it's not a data bit.
SDA low = acknowledge
contacts
well defined
SCL
out of
ISO 7816-1 says 0.76mm
7816 card
at that time
0x0D 0x13
I²C device
at the official reloading desk
they reload it
10€
actually it resets to a default value of 0
I²C EEPROM
the reloading desk only set multiples of 10
the ATmega328P micro-controller on the Arduino
I use the internal pull-up resistors