software for smart card reader writer

August 25, 2006 2:18am CST
IntroductionGO UP This is a Smartcard (ISO 7816) Serial Reader / Writer, also know as "Phoenix" Interface. This adapter must be connected to 9 PIN PC serial port Circuit descriptionGO UP The MAX232 converts the RS-232 levels (about +10 and -10 V) to TTL voltage (0 and +5 V) and vice versa without requiring anything else than +5 V power supply. This chip contains two TTL-RS-232 and two RS-232-TTL drivers and needs four external 1 uF capacitors in order to generate the RS-232 voltage internally. The adapter electronic gets its power supply from the smartcard reader device VCC line or you can use an external 5 V supply if you wish. The card slot's RST line is connected using one of the TTL-RS-232 drivers in the MAX232 to DCD, so that the software and the reader can easily resynchronize in case of a protocol error. The I/O line is a bidirectional half-duplex asynchronous TTL level serial port. We can connect this line to a MAX232 TTL input driver (which is connected to RxD and sends bytes to the PC) in order to receive data from the card. The TxD signal is converted in the MAX232 to TTL level and is connected with an open collector TTL driver to I/O. This open collector driver (one of six in the 74LS07) has a high impedance output during idle state and 1 and is connected to GND during a 0 on it's input. The R4 (a pull-up resistor to +5 V on I/O) guarantees that the adapter is in high impedance state if the TxD line is idle and delivers the correct voltage if the PC sends bytes and the smartcard is in reception mode. As we don't connect totem-pole or tristate outputs to I/O, a short circuit should be impossible in the adapter. Pay attention to the polarity of the capacitors (marked with a + in the diagram next to each capacitor)! The ---- symbols in the MAX232 diagram above indicate the voltage converters inside the chip. The RED LED show you when the reader is powered. The GREEN LED show you the I/O traffic. As a side effect of this simple interface design, every byte sent by the PC is at the same time also received by the PC. Consequently, you can test the circuit with a terminal emulator by switching off local echo: if you still see every typed character immediately on the screen, the interface should be all right. Software must be capable of dealing with this echo from the interface. Components ListGO UP Designator description Value C9 Capacitor 27 pF 16V C8 Capacitor 27 pF 16V R4 Resistor 22 KOhm R1 Resistor 220 Ohm R2 Resistor 220 Ohm R3 Resistor 47 KOhm R6 Resistor 2.2 KOhm R5 Resistor 1 MOhm Y1 Crystal Oscillator 3.579 MHz Quartz U4 Hex Inverter 74HC04N U3 Hex Buffer / Driver with Open-Collector High-Voltage Outputs 74LS07N U2 +5V Powered RS-232 Driver/Receiver MAX232 J1 Serial Connector DSUB 9 PIN FEMALE JP1 Smartcard Connector ISO 7816 DS1 Red LED RED DS2 Green LED GREEN P1 2-Conductor Plug Power Plug +9V / +12V C4 Polarized Capacitor (Radial) 1 uF 16V C3 Capacitor 0.1 uF 16V C2 Capacitor 0.33 uF 16V C5 Polarized Capacitor 1 uF 16V C7 Polarized Capacitor 1 uF 16V C10 Capacitor 100 pF 16V C6 Polarized Capacitor 1 uF 16V C1 Polarized Capacitor 470 uF 16V Elettr. U1 Positive Voltage Regulator 7805 +5V Voltage Regulator S1 Switch Single-Pole, Single-Throw
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• India
19 Oct 06