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TRF7970A: trf7970a irq

gha
Prodigy 100 points
Part Number: TRF7970A

Hi,

I'm developed a board with trf7970a according to the eval board and its connected to a cpu.

First I set the spi Cs to hight, 5ms delay and set the trf7970a EN pin to high (en and en2 pulled via 10k to gnd).

Band gap measured 1.6V, sys_clk is 3.38 MHz, the supply voltage is 5V, the 13.56 MHz osc measured and its fine.

I tried allready two pcb's.

The oscilloscpe is conneted to the irq and on this pin an interrupt is set with a ++ variable but I do not detect any interrupt.

Do you have any idea what can be the problem?

Best Regards,

GH

  • 0
    TI__Guru*** 128125 points
    Hello GH,

    You say "The oscilloscpe is conneted to the irq and on this pin an interrupt is set with a ++ variable but I do not detect any interrupt."

    I don't entirely understand what you mean by this. How is the TRF7970A triggering the IRQ interrupt? Are you configuring the device as an initiator or a target?
  • 0 in reply to Ralph Jacobi
    Prodigy 100 points
    Hi Ralph,

    Thank you for your answer.
    The oscilloscope is connected to the irq pin and set a one shot trigger and do not get a trigger after powering up the system with 5V.
    In the uC I set an interrupt on the irq pin for the trf7970, I initialize irqCntr=0 and in the interrupt I added irqCntr++ and after power up I check this variable in my monitor program and it remains zero.
    It means that I do not get any interrupt after power up the system.

    Best Regards,
    Gábor
  • 0 in reply to gha
    TI__Guru*** 128125 points
    Hello Gabor,

    That is to be expected. You need to do more than just start up the system to get an IRQ.

    The IRQ on the TRF7970A is used to indicate various events related to RFID communication.

    If the device is in an initiator configuration, this includes indicators for sending and/or receiving data, RF communication errors during data transmission/reception, and for ISO15693 specifically a timing indication to handle anticollision slots.

    If the device is in a target configuration, in addition to sending and/or receiving and RF communication errors indicators, there is an interrupt triggered when an external RF field is detected.

    Without first configuring the device as an initiator or target, and then either issuing the correct commands to send data as an initiator or having another 13.56MHz RF field source available (NFC-enabled Android phones can do this) to trigger the RF field detect interrupt as a target, you won't get any IRQ's.
  • 0 in reply to Ralph Jacobi
    Prodigy 100 points
    Dear Ralph!

    Thank you very much for your answer, it was a misunderstanding from my side.

    The other problem is that I do not get any reply from the trf7970a on SPI bus.
    The own developed board connected to a development board via SPI.
    The trf7970a gets the power supply in the same time as the development board.
    ASK and MOD connected to gpio and set to low after startup.
    EN with 10k pull down and connected to a gpio, the EN2 pulled low with 10k.
    Init steps:
    - board power on, ASK MOD EN ChipSelect set to low
    - spi initialization
    - after some seconds I set the ChipSelect to high, delay 3ms, EN set to high, delay 1000ms
    - sending 0x83 and 0x80 values via spi
    - sending 0x8C and try to read 2 values

    The porblem is that I get 0 every time.
    I checked the MISO line with oscilloscope, and I see that the MISO is on 0V level every time.

    Could you mention some for me some ideas what ccan be the problem?
    Thank you very much and best regards,
    GH
  • 0 in reply to gha
    TI__Guru*** 128125 points
    Hello GH,

    Sending a 0x8C would do nothing. 0x0C is not a Direct Command, and if bit 7 is set, then the TRF7970A interprets that as a direct command. Try reading out register 0x0F instead (send command 0x4F which is Read + Register 0x0F) and see if you get a reply there. If the device is up correctly, bit 6 of that register should be set.
  • 0 in reply to Ralph Jacobi
    Prodigy 100 points
    Hello Ralph,

    It looks like, that it was a power up issue.
    I added the pull down to the ASK and MOD pins and connected the VIN from the 5V to the 3V3.
    The 5V comes from the power supply directly and the the 3V3 from the onboard regulator.
    Thnank you very much for the suggestions.

    Best Regards,
    GH