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No stop signal from TDC1000

Chris Cencula38
Prodigy 120 points
Other Parts Discussed in Thread: TDC1000, TDC7200

I've got at TDC1000 and TDC7200 connected like the connections on the eval board.

The pulse train launched from the TDC1000 on the TX line and see the response on the RX line an appropriate time later look OK to me.

I see the start signal from the TDC7200, but don't see the stop signal from the TDC1000.

I'm using the same register settings as on the TDC eval board using the GUI (where I see TX and RX signals that look very similar to what I'm seeing on my board).

Wondering if anyone else has had similar problems?  Most of my component values are identical (or nearly so) to those on the eval board.

Thanks,

Chris

  • 0
    TI__Mastermind 21685 points

    Hello Chris,

    Regarding TDC7200 initializations

    a) >>> SPI_Write_TDC7200(TDC7200_CLOCK_CNTR_STOP_MASK_L_REG, 0x00); // Mask STOP signals for 62uS (.125uS/cycle * 496 = 62uS)
    >>>SPI_Write_TDC7200(TDC7200_CLOCK_CNTR_STOP_MASK_H_REG, 0x00); // high-order counts = 0x01 for 62uS

    FYI, you cannot make STOP MASK registers 0x0. To quote from data sheet, this implies
    “All STOP signals occurring before the value set by the CLOCK_CNTR_STOP_MASK registers will be
    ignored. This feature can be used to help suppress wrong or unwanted STOP trigger signals.”
    This doesn’t explain why you don’t see any STOP on the scope but only says TDC7200 will not recognize any STOP. There still might be some issue in the TDC1000 register initializations.

    b) >>>SPI_Write_TDC7200(TDC7200_CONFIG1_REG, 0x83);
    Here also you need to be careful. Whenever you write 1 to the START Measurement bit, immediately TDC7200 will send a trigger to TDC1000. It’s not a good idea therefore to set this bit when you are in the beginning of register initializations. I would suggest initialize all the registers and finally set this bit to 1 to start a measurement.

    Initially, I would suggest keep the TDC7200 register initializations to default (same as TDC1000_7200EVM), get things working and then play with more involved features like STOP Mask.

    Thanks,Vishy