Smart Card Interface

AN2271

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Smart Card Interface

This interface provides the user with a set of functions for using the Timer and I/O to

communicate with the smart card. It is composed of 3 files:

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HID_usb.c

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UARTT0.c

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Int_7265.c

The HID_usb.c file provides the protocol conversion from the HID protocol to the ISO7816

APDU protocol for the main loop program.

The UARTT0.c file implements the ISO7816 T0 protocol to communicate with the smart

card.

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CardPowerOn() function is called by HID_usb.c to provide a voltage to smart card

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CardSend() function is called by HID_usb.c to start a UART communication

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T0SendData() function is called by timer interrupt to send one bit at a set time

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T0ReceiveData() function is called by timer interrupt to receive one bit at a set time

The Int_7265.c file provides one timer interrupt management and one external interrupt

management to implement the ISO7816 T0 protocol.

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INT_TIM() function is coded to call T0SendData() function or T0ReceiveData() function

to receive or send one bit when a specific time is reached.

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INT_EI2() function is coded to start the timer when a UART start bit is detected.

The MCO pin of ST72651 is used to provide a clock signal to the smart card. The output of

the MCO pin is 6MHz. In this solution, it should reduce to 3MHz to use as smart card clock,

if the user wants another clock frequency, an external crystal could provide different clock.

The UsbVddf pin of ST72651 is used to provide Voltage to the smart card. The voltage

output by this pin is 3.3V, so this interface is 3.3V. If you want another voltage interface, you

should modify the I/O pins.

In this solution, the baud rate of the ISO7816 interface uses a default value of 8.064kbps. If

you require another baud rate, the timer value should be modified.