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RF37S114: RF37S114 and TRF7960, no inventory

Henk Pragt
Prodigy 70 points
Part Number: RF37S114
Other Parts Discussed in Thread: TRF7960, TRF7960A, TRF7970A

Hi,

I am trying to get a board working that is equipped with a TRF7960ATB evaluation module, to read and write RF37S114 transponders. Communication with the TRF7960 is OK, and it switches its transmitter on and off as required, and reading the registers back give correct data. However, it only returns TX ready and No Reponse interrupt status. Since there will be just one transponder near the antenna, I use single slot operation: 8F 91 3D 00 30 26 01 00.

Can anyone please tell me if this should work with the RF37S114 while the TRF is programmed for ISO15693, or should I program it for the tag-it protocol? If so, what is the correct setting? Any other suggestions? Thx. Henk

  • 0
    TI__Guru*** 135355 points
    Hello Henk,

    The RF37S114 is fully compliant for ISO15693 and will work with the TRF7960A. I've read that tag with the 60A many times.

    How close to the antenna of the TRF7960ATB is the RF37S114 tag placed?
  • 0 in reply to Ralph Jacobi
    Prodigy 70 points
    Hi Ralph,

    thanks for your quick reply. I tried any distance from immediately on the antenna board up to 20cm. I also tried the tag-it labels supplied with the TRF7960ATB, but never got anything else than No Response timeout. I also tried different delays after activating the RF field, and various register settings. All registers are at their power-on defaults, except ModulatorControl which is 0x91 in stead of 0x11, and TXPulseLenghtControl which is 0x00 in stead of 0x80 as recommended for ISO15693, but setting that register also did not help.

    Can you perhaps help me to a list of all register settings for this tag? That would take away lots of blind guessing.
  • 0 in reply to Henk Pragt
    TI__Guru*** 135355 points
    Hello Henk,

    You will definitely want to leave the tag close to the board. On top of the antenna is best. With the TRF7960ATB you probably can get ~1 cm range, but definitely not much than 2.

    Regarding register settings, please refer to this firmware example: www.ti.com/lit/zip/sloc297

    That firmware defaults to the TRF7970A but you can change that by changing the #define TRF79xxA_VERSION in trf79xxa.h from 70 to 60 which should make the relevant section easier to read.

    You will want to make sure you configure the device as outlined by TRF79xxA_initialSettings and then check the Register settings for Case 0x02 in TRF79xxA_setupInitiator.

    Some of the registers do not take the default values when the appropriate protocol is chosen in the ISO Control register, so that may be the issue - the firmware example I shared sets the registers that are affected.
  • 0 in reply to Ralph Jacobi
    Prodigy 70 points

    Hi Ralph,

    thanks for the source code: it is a lot better than others I have studied. I modified the initialisation to match yours, the voltage on the antenna jumped to 30Vpp, and presto: tags are being discovered correctly.

    About your remark on the detection range: the tags will be in juice containers at a distance of 1cm from the interface board. Currently, the ATB board is reliably detecting them. However, the ATB antenna seems rather oversized in comparison with the tiny RF37S114. In the final design of the interface I would like to reduce the size of antenna to e.g. 10mm (15mm diagonally). Do you reckon that would work?

    thx, Henk

    . 

  • 0 in reply to Henk Pragt
    TI__Guru*** 135355 points
    Hello Henk,

    10mm square would work pretty well! We did a study on this and it's posted as an app note I think you will find very helpful for your application: www.ti.com/.../scba035a.pdf

    Table 4 on Page 5 has a listing of antenna sizes vs read range.

    It will be important that the TRF7970A is operated at 5V for your system to maximize read range, just as an FYI!