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TDC1000-TDC7200EVM: Doubts in GUI settings.

Prudhvi Sagar
Genius 3785 points

Part Number: TDC1000-TDC7200EVM

Hello,

What is meant by the option AVG/STDEV NUM_ELEMENTS(>0)? In TDC_SELECT what is the best option be selected for the flow application, currently my readings are fluctuating a lot. Can this only be selected experimentally?

Regards,

Prudhvi Sagar

  • 0
    TI__Mastermind 31655 points
    Hi Prudhvi,

    This just determines how many points are averaged for the TOF AVG Value display above, and the total number of elements used for the standard deviation calculation. A larger number will average more samples and show a more stable TOF AVG Value and a smaller standard deviation.

    This only affects the display of the data, and will have no impact on the actual TOF points that are ready by the TDC1000/TDC7200.

    Regards,
  • 0 in reply to Scott Cummins
    Genius 3785 points
    Hello Scott,
    Ok, so the data in the excel sheet is independent of the option we select?

    Can you tell me how to select the TDC_SELECT. Selecting the Stop option is done experimentally only?

    Regards,
    Prudhvi Sagar.
  • 0 in reply to Prudhvi Sagar
    TI__Mastermind 31655 points
    Hi Prudhvi,

    Correct. The CSV file will only have the raw data points. You have to calculate the AVG and STD on your own from those points if you would like to.

    TDC_SELECT shows which STOP time will be displayed on the graph. START-STOP1 through START-STOP5 are all the single times. START-STOP123 through START-STOP345 are each averages of the times. For exacmple START-STOP123 is the average of START-STOP1, START-STOP2, and START-STOP3. The CSV file includes the data for each of the START-STOP1 through START-STOP5 values.

    These functions are only added for experiments in the GUI as you mention. You can easily implement these in your data post-processing if your application calls for it. However, these functions are not a part of the data from the TDC7200 directly.

    Regards,
  • 0 in reply to Scott Cummins
    Genius 3785 points
    Hello Scott,
    There is an option for TDC1000 called NUM_AVG which says that it allows the MCU to performavergae of multiple TOF measurements. Is this option a similar kind of averaging. There is an averaging happening in TDC7200 aswell which I havent understood. Can you please throw some light on that topic. Thank you for the support.

    Regards,
    Prudhvi Sagar.
  • 0 in reply to Prudhvi Sagar
    TI__Mastermind 31655 points
    That is multi-cycle averaging which is described in the datasheet. It will average the values of the selected number of measurements in the TDC7200 and output them, but it will only average the TIME and CLOCK_COUNT values that match. So you can get the average of a certain number of START-STOP1 values, but you cannot average START-STOP123 like the GUI does. It will be impossible to calculate the STD values since the individual points are not recorded, and there is no STD output from the TDC7200.

    The multi-cycle averaging is useful for smoothing the data, and will reduce the number of data reads required by the microcontroller. The microcontroller can stay asleep until all the measurement cycles have been completed.
  • 0 in reply to Scott Cummins
    Genius 3785 points
    Hello Scott,
    Thank you for the quick response Scott.

    Is the measurement taking place at TRIGGER UPDATE FREQUENCY? IT shows the least it can goto 100ms. Can this be reduced further in the code? so that the full it can be approximately the size of each measurement taking place?

    Regards,
    Prudhvi Sagar.
  • 0 in reply to Prudhvi Sagar
    TI__Mastermind 31655 points
    Hi Prudhvi,

    The trigger frequency option determines the rate of measurement. It is limited to once every 100ms because of the slow USB communication between the GUI and the EVM. In practice this rate can be higher, but not with the EVM.

    The highest measurement frequency in a standalone system depends on the TOF and the SPI communication frequency, since the TOF data must be read from the TDC7200 before starting a new measurement and clearing the data registers.

    Regards,
  • 0 in reply to Scott Cummins
    Genius 3785 points
    Hello,
    So by using NUM_AVG and AVERAGING CYCLES we get the average TOF for only START-STOP1 or for any of START-STOP2, START-STOP3, START-STOP4 etc or does it average all of the above TOFs? I can on top of this use MCU to average START-STOP1,2,3 etc.

    Regards,
    Prudhvi Sagar
  • 0 in reply to Prudhvi Sagar
    TI__Mastermind 31655 points
    From my post above:

    "TDC_SELECT shows which STOP time will be displayed on the graph. START-STOP1 through START-STOP5 are all the single times. START-STOP123 through START-STOP345 are each averages of the times. For exacmple START-STOP123 is the average of START-STOP1, START-STOP2, and START-STOP3. The CSV file includes the data for each of the START-STOP1 through START-STOP5 values. "

    If you select START-STOP1 it will only average the START-STOP1 values over time.

    Regards,
  • 0 in reply to Scott Cummins
    Genius 3785 points

    Hello sir,

    My doubt was regarding NUM_AVG and Multi cycle averaging. Can these setting give only single times of all stops or only STOP1?

    Regards,

    Prudhvi Sagar

  • 0 in reply to Prudhvi Sagar
    TI__Mastermind 31655 points
    The NUM_AVG setting only affects the GUI. It determines how many samples of the time of flights that are output by the EVM to average before displaying the value in the graph tab. You will see the average for whichever START-STOPx time you select with the TDC_SELECT.

    Multi-cycle averaging occurs in the TDC7200. It will average however many samples you select after running that many measurements in a row. This averages the values in the TIMEx and CLOCK_COUNTx registers in the TDC7200. The result is that the time of flight calculated from those registers will be an averaged value of START-STOPx.
  • 0
    Genius 3785 points

    Hello,

    Thank you for the support. NUM_AVG is an option of TDC1000, how can it only effect only the GUI.

    Regards,

    Prudhvi Sagar

  • 0 in reply to Prudhvi Sagar
    TI__Mastermind 31655 points

    Sorry, I mixed up the NUM_AVG setting with the NUM_ELEMENTS on the GUI graph tab. NUM_AVG is only used in Mode 2 and it lets the TDC1000 know how many measurements to take in one direction before switching directions.

    The full description is easily searchable in the datasheet:

  • 0 in reply to Scott Cummins
    Genius 3785 points
    So NUM_AVG of TDC 1000 has to be synced with multi averaging of TDC 7200 to get the proper results.

    Regards,
    Prudhvi Sagar