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Hi guys, here is my question;
if I have a tag that is working at a custom frequency (probably 3 or 6 MHz) but I am pretty sure that the communication protocol is the same as another 125kHz product, will I be able to use an already implemented 125kHz command (ex. "lf read") changing only the coupling antenna or should I have to write a new code in PM3 ?
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For LF carriers you can change the divisor using function(armsrc)
FpgaSendCommand(FPGA_CMD_SET_DIVISOR, XXX);
where XXX is divisor number.
You can use following formula to calculate carrier frequency
12Mhz/(divisor+1)
For example you want to set it to 125 khz:
12Mhz/(95+1)
This is similar to
FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 95);
Another LF example:
FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 88); //134.8Khz
You can set it up to 600 khz.
For HF you probadly can change carrier frequency by modifying FPGA code i.e. dividing ck_1356meg signal in the way like generating a subcarrier from external reader's clock.
13.56/2=6.78
13.56/4=3.39
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Thank you for your quick answer vivat! Do you think Is it possible to implement this kind of hf function for 4150 lf protocol tags?
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Can you give more details?
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I have a tag that probably is 3 or 6 MHz made by EM Microelectronics but I am pretty sure that it uses a communication format simil if not identical to lf EM41x0 tags so I would like to read it using PM3 already implemented commands and my HF antenna... will it be possible ?
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No, I don't think so because as you said in your post, the carrier frequency is 3 or 6 MHz. Proxmark can generate 13.56 mhz carrier, try to divide it by 2( or 4). IMHO Without touching the code and making better antenna it is impossible.
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