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Can I use the transponder base station TMS3705A to read Texas Crypto 128 bits tranponder ?

Daniel Flor
Prodigy 50 points
Other Parts Discussed in Thread: TMS3705, TMS37145

I need to read a Texas Crypto 128 bits transponder using a TMS3705A, but it is not working. To do this I will need to change the write bit temporization in the antena, but when I change the Toff and Ton of the bits high and low in TXCT, the correspondent change doesn't occour  in the antena. Please, can someone give a tipo or something ?

Thanks.

  • 0
    TI__Guru* 91146 points
    you have #defines like this set up in your .h file?

    // Default ON and OFF Times for High and Low bits
    #define T_OFF_L 120
    #define T_ON_L 880
    #define T_OFF_H 480
    #define T_ON_H 520

    // Default ON and OFF Times for High and Low bits RW
    #define RW_T_OFF_L 300
    #define RW_T_ON_L 1700
    #define RW_T_OFF_H 1000
    #define RW_T_ON_H 1000
  • 0 in reply to Josh Wyatt
    Prodigy 50 points
    Yes, I used the first definitions of time that you said and it doesn't work, so I used the second definition, RW, that you wrote, and the microcontroler sends the command via TXCT, but it isn't modulated on antenna.
  • 0 in reply to Daniel Flor
    TI__Guru* 91146 points

    what are you trying to send? which transponder is it? what is your setup exactly? do you have pictures, schematics, etc?

    can you try the simple things here like what i have here to ensure you have control over the device?

    5123.Notes on TMS3705A1DRG4 & Read.pdf

  • 0 in reply to Josh Wyatt
    Prodigy 50 points
    I don't have a schematic, I'm trying to send a command of 20 bits that is sent to the tranponder to identify it. I saw this command by using a osciloscope on a base station that can identify it. The transponder model is recognized as Texas Crypto 128 bits H. I already read others transponder with TMS3705, however, I cant identify the Texas Crypto 128 bits. I think it happens because I don't know how to change the bit period times on the rfid antenna.
  • 0 in reply to Daniel Flor
    Prodigy 50 points 
    |<-----TbitH-------->|
                ________                      
                |                 | 
_ToffH__|   TonH    |__

    To Bit 1

    TbitH: 560 us
    ToffH: 210 us
    TonH: 350 us

    To bit 0:

    TbitL: 430 us
    ToffL: 210 us
    TonL: 220 us

    But, when I send this bit in TXCT, the periods that appear on rf antenna are not related.

  • 0 in reply to Daniel Flor
    TI__Guru* 91146 points
    do you have a o'scope capture?
    are you able to read other tags?
    the name you are using is not familiar
    we only have the TMS37145 devices which are backwards compatible with DST80 and add AES - is this the tag you are using?
    if you don't have schematic of the reader and MCU, how are you writing code for it?
  • 0 in reply to Josh Wyatt
    TI__Guru* 91146 points
    further - this document has proven invaluable to developers over the years - www.ti.com/.../scbu052.pdf
  • 0 in reply to Josh Wyatt
    Prodigy 50 points

    Thank you Josh Wyatt, this document really is a good reference. About my application, I can say that I need to implement a system that can identify transponders HDX FSK, 134.2Khz, so, I'm using TMS3705 for it. I already can identify another transponders like Texas DST 4D, but I found a transponder that is knowed like Texas Crypto 128 bits H, I think that this isn't the Texas name of it, but I don't know the real name of it.

    I doesn't have the schematic, I can write code because I already have an API that allows me to abstract a bit the hardware detail. I just need to implement a driver to read a especific transponder.

    Like I said before, I used a osciloscope to verify the command used by a base station that can identify this transponder, so, I measured the bit times, and tried to send a command to TMS3705 varying the times Toff and Ton, to reproduce this pattern, but it didn't work. In the datasheet of TMS3705 the values of time to ToffH, TonH, ToffL and TonL are given and seems to be fixed. So I was wondering if the TMS3705 can really read it.

    I'm not sure if this transponder model uses AES encryption, but, I just need to implement identification of it. About the model you indicated, TMS37145, from what I could see, it uses a 80-bit encryption algorithm and not 128.