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TDC7201: Appropriate read time

Winnie Lee
Intellectual 1205 points
Part Number: TDC7201

Tool/software:

Hi expert,

We read the status register every 3us. What effect would this have (including the read results)? How often would it be appropriate to read?

  • 0
    TI__Mastermind 23045 points

    Hello Winnie,

    Thanks for posting to the sensors forum! There really isnt an ideal time for reading the TDC7201, since obtaining results depends on the timing of external sources which could take even longer than 3us. User's should be monitoring the INTB pin as this pin indicates when results are ready to be read from the device.

    If the registers are read during a measurement the device will abort the measurement and some of the result registers will not have the appropriate values stored in them.

    Best,

    Isaac

  • 0 in reply to Isaac Lara
    TI__Intellectual 1205 points

    Hi Isaac,

    If the distance is two meters, how long does it take to measure? How do I calculate it?

    Best Regards,

    Winnie

  • 0 in reply to Winnie Lee
    TI__Mastermind 23045 points

    Hello Winnie,

    You can calculate the expected ToF using the following formula, ToF= (2*distance)/(speed in medium). I am not sure what the speed of sound is in your medium, but note that the device still needs additional time to process the data so measuring the INTB is still the best method to indicate when the device has the data ready to be read.

    Best,

    Isaac

  • 0 in reply to Isaac Lara
    TI__Intellectual 1205 points

    Hi Isaac,

    I used mode 1, and I captured the value of calibration registers 1-2 that changed a lot over time. Registers use the default configuration. I go back to see if the interrupt register has an interrupt before I read the data every time. After reading the data, I will configure register config1 to restart the measurement.


    Best Regards,

    Winnie

  • 0 in reply to Winnie Lee
    TI__Mastermind 23045 points

    Hello Winnie,

    The best method is to use the interrupt pin on the device. Like I mentioned above any communication even reading the interrupt register while a measurement is occurring will stop the active measurement you are performing.

    Regarding the shift in the data you are seeing, is there a temperature difference in your medium? How often are your readings? The change seems very sudden based on the images but then remains stable at that new value so I am wondering if something else is changing.

    On the two captures you provided are these two separate runs? It seems like the change happens at the exact time which I find a bit strange.

    Best,

    Isaac