Title : PC to VideoCrypt and/or Smart Card interface via RS232 port. The following interface has been built and used succesfully. It is loosely based on Markus Kuhn's ADAPTER.TXT and can be used in three modes: * PC listens to traffic between VideoCrypt decoder and Smart Card. * PC pretends to be the Smart Card and talks to the VideoCrypt decoder. * PC pretends to be a VideoCrypt decoder and talks to the Smart Card. 3 5 8 VCC oÄÂÄÄÄÄÄÄÂÄÄÂÄÄ¿ ³ ÚÄÁÄÄÁÄÄÁÄ¿2 100 ÍØÍ 1Ä´ EXO-3C ÃÄÄo CLK output nF ³ ÀÄÂÄÄÂÄÄÂÄÙ GND oÄÁÄÄÄÄÄÄÁÄÄÁÄÄÙ 4 6 7 Qty Part Package Description 1x EXO-3C DIL 8 Programmable Oscillator 14.31818Mhz max frequency CIRCUIT DESCRIPTION The interface is designed to be connected to a PC with a 9 pin or 25 pin RS232 port. The PC's RS232 port operates with signals that swing from +12V to -12V. The smart card however, operates with TTL signals that swing between +5V and 0V. An RS232 -12V level corresponds to a TTL high (+5V) and a RS232 +12V level corresponds to a TTL low (0V). Due to this incompatibility, a signal level translator such as the MAX232 must be used. The MAX232 is powered from a single +5V supply and generates internally the +/-12V voltages necessary for the RS232 communication. The MAX232 needs external components to achieve this. The DCD line is used to monitor the state of the RST line on the smart card. This allows us to detect when a reset takes place. The RXD line is used to receive data from the smart card. All TTL signals from the MAX232 go to SC1 which is a smart card connector accepting cards with contact locations that conform to the ISO7816-2 standard, section 4, fig 2. The final part of the circuit is a oscillator. This is only needed if you intend to have the PC exchange data with a smart card. At all other times the oscillator must be disconected. In the prototype the oscillator was built on the board and a jumper is used to connect or diconect the oscillator output to the card's CLK pin. There are many options for building oscillators. Some people use discrete components. This Osc is a programmable frequency divider. This is a DIL 8 pin chip with a built in crystal oscillator. The one in this project has a base frequency of 14.31818Mhz. Three pins on the chip allow a divisor between 2^1 to 2^8 to be selected allowing frequencies between 7.15909Mhz and 55.93khz to be produced. A separate output, provides the undivided base frequency. In this project a divisor of 2^2=4 was selected effectively providing an output frequency of 3.579545Mhz. Oscillators are really noisy devices. They produce a lot of noise on the power line. Therefore, a 0.1 uF capacitor _must_ be fitted as close to the supply lines of the oscillator as possible. This not only eliminates the noise on the supply lines but improves the sqareness of the generated waveform. Total current drawn at 5V with oscillator active is 7.6mA. WARNING: Before attempting to connect the interface to any decoder, use a high impedance DMM to measure the AC voltage difference between the interface GND and the decoder's GND. If the difference is not close to 0VAC, earth the decoder's GND before connecting the interface. Use at your own risk. If you damage something you have no one to blame but yourself for stuffing with it in the first place. Take care. Regards paul