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TRF7970A: TRF7970A Ultra Low Power Question

Rick Neufelder
Prodigy 20 points
Part Number: TRF7970A
Other Parts Discussed in Thread: MSP430F2370, MSP430G2553

To meet our products physical size constraints, we implemented the Hardware design from the TRF7970AEVM (MSP430F2370 and TRF7970A NFC IC) including the card sniffer items into our product instead of the newer DLP EVM design. We do not have the older EVM since it’s no-longer available.

We loaded the sloa184 code into our hardware, and found it to be unstable, and we could not read our ISO15693 tags properly. This code did appear to be performing the low power operation since we observed sleep wake cycles and RF activity that matched the sloa184 application note. We need the low power operation stated in the sloa184 app note to meet our product requirements.

We found the sloc297c.zip code which address many of the issues with the sloa184 code, and ported it from the MSP430G2553 that it was configure for, to our MSP430F2370 micro, and are able to read tags properly. This code does not appear to have the low power operation that the sloa184 code had.

What is the best strategy to get low power operation working with the sloc297c code base?

  • 0
    TI__Guru*** 134965 points
    Hello Rick,

    It sounds like you've stumbled upon the same conundrum I had a few years back...

    Due to the performance of sloa184 as far as tag reading goes, I also had looked into porting the ULP example into the SLOC297 myself, and unfortunately I have to confess that I ran into a lot of challenges in doing so and the project was eventually dropped before I made a breakthrough.

    A lot of the challenges are because the engineer who designed the hardware and wrote the software for that app note is no longer with TI.

    If I am remembering right, the challenge I was running into is trying to trigger the reads successfully. I recall being able to validate the individual pieces on their own. I could detect the presence of a tag via ULP detection and wake up. And I could read a tag if starting from normal power mode without ULP wake. What I couldn't quite get to fit together was waking from low power mode and then moving to read the tag.

    As far as a strategy goes, I feel I was mostly on the right path, there was just something which didn't click together.

    I would recommend using SLOC297 as the basis to start, and then look into integrating the ULP wake functionality as an API which once it returns a true for tag detected, then calls the RFID read routine. In other words, keep RFID reading APIs as one set of calls, and ULP wake as another. I think keeping these functionalities separate is the way to go, and just use the return of a ULP wake API to trigger when to begin with the RFID reading routines.

    If you want, I can share what I have done before, but I am not sure it's quite helpful because
    1) It was done on an older version of SLOC297 which had bug fixes and improvements since
    and
    2) The main benefit is that the ULP functionality had been ported to the G2553, but if you are using an F2370 then you wouldn't need to port that.

    Also just looking back at what I had done, I can see some logical flaws in the way I had programmed the process... but anyways, if you feel it could be helpful I don't mind sharing.
  • 0 in reply to Ralph Jacobi
    Prodigy 20 points
    Ralph, I would like to take you up on your offer of working with your modified code. I think this will save us a few steps. If possible, please send the the older SLOC297 that you started with so I can review the direction that you were going. And thanks for the detailed strategy steps.

    Regards,

    Rick Neufelder
  • 0 in reply to Rick Neufelder
    TI__Guru*** 134965 points

    Hello Rick,

    Okay here is the project: 

    TRF7970ABP_ULP_Reader_Demo.zip