I'm trying to implement a sim-card reader for my own. I followed step by step the guide on www.ladyada.net site but it does not work as it would be. My PC and softwares i used to read/write data from/to sim-card could't recognize my sim-card reader. Have someone successfully made this sim-card reader circuit? Pls help me with some ideas or show me where i went wrong. Thanks so much. P/s: this is the circuit schematic in .png Sim Card Reader Circuit

And this is the site i followed: Reference Link

  • You said "My PC and softwares i used to read/write data from/to sim-card could't recognize my sim-card reader"
    What did you expect?
    It is a very simple terminal circuit using a RS232 interface to send and receive data. There is nothing to recognize, e.g. no reader ID...
  • Another thing you have to consider: the data line is bi-directional, i.e. there is one line for transmitted and received data. Therefore your commands sent to the card will be echoed back, which is not a problem as the terminal software knows what it has sent; but it has to be handled. I.e. the terminal software has to remove the echoed command from the received data.
  • This simple kind of reader will not be able to handle communication errors according to the T=0 communication protocol, which is used for SIM cards. According to T=0 the receiver must signal a transmission error (parity error) by pulling down the data line for 1 ETU shortly (i.e. 0.5 ETUs) after receiving the bad data frame. Standard UARTs have no possibility to do that (ETU = "elementary time unit" = duration of one bit).

You definitely can not expect any random software to be able to use your simple terminal. It has to be specialized for this reader.

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You do not give nearly enough information to answer the question, so here are common problems from website's FAQ http://www.ladyada.net/make/simreader/faq.html"

1. You have the wrong COM port selected (make sure you have this right)
2. Your serial cable is damaged or is the wrong kind (say its a null modem cable, which is not correct)
3. You have a soldering error in any part of the kit (go over your kit)
4. The SIM holder is on backwards (check the photos carefully)
5. The SIM is damaged (test it with a phone to see if its a working SIM)
6. The SIM is not compatible with being read for some reason (unlikely)

I can add that there is a simple way to check if the problem is with soldering error (1-4) vs bad SIM card(5-6):

  1. Remove sim card
  2. Power up the device. Measure the voltage on SIM card holder relative to black battery wire:
    • Pin 5 (GND) must have 0 volt
    • Pins 7 (I/O) and 1 (VCC) must have 5 volt
    • Pin 3 (CLK) must have something between 0 and 5 volt. Maybe the number will change continuously. It should NOT be always 0V or 5V.
  3. Open terminal connected to serial port. Use low speed such as 9600 baud.
  4. Type anything into terminal. It should be echoed right back.
  5. Use a piece of wire to temporary connect GND and I/O together (pins 5 and 7 on sim card holder). Tap the I/O pin while watching the terminal. This should produce garbage-looking characters on screen.
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