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JPehl.1
JPehl.1
Associate III
August 11, 2020
Solved

ST25R95 to wake up a STM32 from sleep mode?

  • August 11, 2020
  • 3 replies
  • 1388 views

Hi.

My board have a STM32F070CBT6TR MCU connected to a ST25R95 NFC transceiver.

I would like to know about the possibility of using the ST25R95 to wake up the STM32 from sleep mode when a tag/field be placed near the antenna of the transceiver.

Pin 12 / IRQ_IN of ST25R95 is connected to PC14 of STM32, and pin 14 / IRQ_OUT of ST25R95 is connected to PC13/WKUP2 of STM32.

Consider that both ICs are constantly supplied with 3.3V, then after some timeout the STM32 will enter in sleep mode. Then, I would like the ST25R95 could wake-up the STM32, (maybe through IRQ_OUT or other pin), while the STR25R95 consumption be lower when there is no NFC tags near to my PCB.

Is that possible? If yes, how?

Or in order to have such functionality I would need to change the transceiver (which part number)?

Is there any way the ST25R95 can be configured via SPI to do such thing? (generate a level change on any WKUPx pin of STM32 when a tag is placed close to the antenna?)

I am still unclear after checking the datasheet.

OBS: I have not done prototypes of this board yet, so I can still change the layout.

OBS: The antenna is double layer, there is 5 turns on each side of the board.

0693W000003Oz5WQAS.png

Regards.

    This topic has been closed for replies.
    Best answer by Ulysses HERNIOSUS

    Hi Jeferson,

    from perspective of ST25R95 these connections looks right.

    From the DS:

    "

    Wake-up by tag detection

    In this mode, the typical consumption varies widely in function of parameter settings (WU period without RF

    activity and Swing Count defining the RF burst duration). Using default settings, consumption in the range of 100

    μA can be achieved.

    "

    I guess it will also depend on your antenna and matching on how much current is flowing through it while issuing the measurement pulses.

    Regards, Ulysses

    3 replies

    Ulysses HERNIOSUS
    Ulysses HERNIOSUS
    ST Technical Moderator
    August 12, 2020

    Hi,

    the ST25R95 supports an idle command which lets you specify among others sources : Tag Detect and IRQ_IN as sources.

    If the tag detection is calibrated before then issuing a proper Idle command will put the ST25R95 into a low power state where it will signal on IRQ_OUT that a wake-up event has happened (e.g. a card changing the LC tank). It is advisable to also set IRQ_IN as source to be able to allow the MCU to move the ST25R95 out of this state without a detected a tag.

    The needed procedure are implemented inside STSW-ST25RFAL003 and are demo'ed in e.g. X-CUBE-NFC3.

    Best Regards, Ulysses

    JPehl.1
    JPehl.1Author
    Associate III
    August 12, 2020

    Thanks Ulysses.

    So my need (wake up the STM32 through a tag detection on ST25R95) is possible to make, correct?

    I have connected IRQ_OUT of ST25R95 to WKUP2 of SMT32, and there is a GPIO of STM32 connected to IRQ_IN of ST25R95.

    What is the expected current consumption when no tag is nearby? @ 3.3V...

    I just wanted to know if with my current hardware the functionality would work, Yes or No... Firmware is later, now I am only asking about hardware possibilities.

    Regards, Jeferson.

    Ulysses HERNIOSUS
    Ulysses HERNIOSUSBest answer
    ST Technical Moderator
    August 13, 2020

    Hi Jeferson,

    from perspective of ST25R95 these connections looks right.

    From the DS:

    "

    Wake-up by tag detection

    In this mode, the typical consumption varies widely in function of parameter settings (WU period without RF

    activity and Swing Count defining the RF burst duration). Using default settings, consumption in the range of 100

    μA can be achieved.

    "

    I guess it will also depend on your antenna and matching on how much current is flowing through it while issuing the measurement pulses.

    Regards, Ulysses

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