Attention!!!
This circuit its only a reader its not programmer. You CANNOT refill, hack or any illegal thing, the telecards. The purpose of this circuit its to understans how a microcontroller read, serial, the telecard, to build some other circuits like "electronic safety lock", "Checker for how much units left in the card" etc.
Introduction:
This reader can read the contained memory of the telecard. This cards have 64 bytes ( 512 bits) of eeprom memory that the first 8 bytes ( 64 bits ) is write protected, its only for reading. This circuit does not include any lcd display, to keep the cost low, but the data can be viewed to any PC system using the RS232 port, by the Hyper terminal software.
The circuit:
The circuit based on AT90S2313 AVR microcontroller from atmel, programmed with telecard.hex and telecard.eep . The converter from + - 12V of RS232 to TTL and from TTL to + - 12V is MAX232. When you build the circuit ( i think its very simple ), connect the reader with RS232 port of the PC, run the Hyper terminal software ( start – programs - accessories – communications – Hyper terminal ) and set the baud rate to 19200 bps 8 none 1.
Power on the reader, insert the telecard and press the switch to read the contain of the card.
If you use a telecard base, usually this base its include a switch that is pressed when you insert the card. You can use this switch, to make the reading of the card, automatic.
Snapshoot of Hyper terminal window
Picture of a Greek telecard
The contain of the above telecard
Memory map for Greek telecards:
The 1st (85) and 2th (FC) byte it’s the country. The 3th (0B) is the units (3000) and 4th is the customer (OTE). This results are from the testing of 50 different Greek telecards and i don’t know if there are correct.
The 5th, 6th, 7th and 8th bytes are the serial number of the card in hex form. If you convert the 4A037AA0 hex ( bytes 8 to 5 ) to decimal, you will get the number 1241741984 ( look the serial number of the black telecard above ) .
The 9th, 10th, 11th, 12th and 13th bytes are the units left counter, 5 stage octal counter that is counting the units to the zero (0).
Source, hex and schematic if you use AT90S1200
Source, hex and schematic if you use AT90S2313
For more informations about how the telecards working
