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Mark Schwab
Prodigy 235 points
Other Parts Discussed in Thread: TRF7960

I've read a whitepaper called P-MTI: Physical-layer Missing Tag Identification via Compressive Sensing

The link is here http://pdcc.ntu.edu.sg/wands/yqzheng/papers/P-MTI-TON.pdf

I want to send a one slot inventory request and have multple tags respond at once.  When there is a collision is there any information available?  I want the UUID number after the collision.  I'm using the TRF7960 with custom firmware.

  • 0
    TI__Mastermind 38620 points

    Hi Mark,

    This is an interesting paper and question.  We typically just receive a collision error interrupt when a single slot inventory is sent with multiple tags in the field.  We never read the FIFO after this, so I am not immediately sure if any useful UID data is available.  We will test this tomorrow and let you know. 

  • 0 in reply to Eddie LaCost
    TI__Mastermind 38620 points

    Hi Mark,

    Unfortunately, the TRF79xx will not provide any useful UID data when sending a single slot inventory command and collisions occur.  Single slot is really intended to consider any collisions as a failure, so there is not additional data available. 

  • 0 in reply to Eddie LaCost
    Prodigy 235 points

    Thank you for checking.

    Have you tried in Mode 0?  I'm trying to frame a packet in Mode 0 and try to read it back in Mode 0.  If that doesn't work I'll try an envelope detector on Pin 12.  I think that the idea has potential.

  • 0 in reply to Mark Schwab
    TI__Guru* 91086 points

    Mark - 

    we tried it in Direct Mode 2, with two tags - seeing the collision and then reading out the FIFO, then trying to correlate it to either one of the UIDs - no luck there.

    you may have better luck just having a look at / decoding what is on MOD pin when using the setting in the test register 0x1A for making that a digitized output

    keep us updated if you end up finding something out cool or otherwise.

    it does seem like an interesting paper - i think i will read it a couple more times, too - its packed with alot of detail 

  • 0 in reply to Josh Wyatt
    Prodigy 235 points

    Thanks Josh,

    I just read about the MOD pin also.  It shares the MISO pin.  Will I have SPI read functionality when I write 0x1A to the test register?  Will I be able to write to the register again to reenable SPI or would I have to change disable the enable pin and take it high again?
  • 0 in reply to Mark Schwab
    TI__Guru* 91086 points

    the use i am describing does not kick the IC into DM0 or DM1, you would get subcarrier output there. this includes SOF to EOF...on the MISO pin you would see only the data, as the IC would check and strip off the SOF, the CRC and the EOF for you.

     

  • 0 in reply to Josh Wyatt
    Prodigy 235 points

    should the data on the mod pin be a steady stream of 0s with the rf field active?  The only reason I ask is because I'm getting a lot of random 1s and 0s without any tags in the vicinity and I have the AGC off and gain reduction turned up with half power output.  

    I'm not sure what the subcarrier output should look like is part of the problem.  If I turn off the transmit on the TRF the subcarrier is all 0s.  I'd expect the subcarrier to be all 0s with the output field active also..

    Thanks again for the support.