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TDC7201: Averaging trigger rate

user5989766
Prodigy 150 points
Part Number: TDC7201

How long time?   ---- 1st trigger between 2nd trigger.

On 128 average and single stop mode,

How many trigger pulse come from TDC7201?

I'm using TDC7201EVM.

Only one trigger pulse come from TDC7201EVM on 128 averaging.

So I send 128pair Start & Stop pulse every 5usec.after trigger.

 

I want send 128pair Start & Stop pulse more quickly , Eg. 2usec.

But averaging failed at send rate 2usec.

 

I want know about fastest averaging rate on 2,4,8,16,32,64,128 averaging and  why only one trigger comes from TDC7201EVM on  averaging mode.


Thanks

  • 0
    TI__Expert 3450 points

    Hello,

    Please try uploading the image again with the 'insert media' button, I cannot see it. 

    The operation of the TDC7201 should follow the explanation in the datasheet:

    A couple things to note are: the time between the last STOP and the next TRIG (or INTB) can take up to 2 us, and the minimum time requirement between TRIG and START rising edges is 5ns. To determine the minimum measurement rate you can run a measurement and measure the actual time between the last STOP and TRIG. 

    If there is a certain measurement rate threshold causing the measurement to fail, please note this and provide a screenshot from your oscilloscope. 

    Also on a failure, check to see if there is calibration data in the TDCx_CALIBRATION1 and TDCx_CALIBRATION2 registers. 

    More information: Start and stop sequence, Measurement Sequence Timing

    Regards,

    Gabriel

  • 0 in reply to Gabriel Lake1
    Prodigy 150 points

    Thank you for your answer.
    It turns out that more than 2usec is needed from the stop pulse to the next trigger.

    When using the averaging function, is there only one trigger regardless of the number of averages?
    Or does it trigger the average number of times?

    For example, please tell me the number of triggers that occur when averaging 128 times.

  • 0 in reply to user5989766
    TI__Expert 3450 points

    From the Multi-Cycle Averaging section of the data sheet:

    128 cycles should produce 128 TRIGGx pulses. 

    Regards,

    Gabriel

  • 0 in reply to Gabriel Lake1
    Prodigy 150 points

    Thank you for your answer.
    With the TDC-7201 EVM, the trigger only occurs once when averaging 128 times. Therefore, 128 start and stop pulses are burst-transmitted for one trigger to operate.

    What settings should I make to generate 128 triggers on the TDC-7201 EVM?

    Then I understood that the time from the stop pulse to the next trigger is more than 2usec, but does that 2usec have to consider temperature fluctuations? I want to know the maximum value.

    Regards,

  • 0 in reply to user5989766
    TI__Expert 3450 points

    Hello,

    The 2us I was referring to earlier is from STOP to INTBx asserting low in a normal measurement. I am not sure how this timing differs in multi-cycle average mode from the last stop to the next TRIGG, so that will have to be determined experimentally, and the maximum measurement rate with depend on this. 

    I am not aware of settings that would interfere with multi-cycle averaging, it should work with any device operating mode. Have you seen the issue with other AVG_CYCLES values? Can you provide more details on the issue: a scope plot that summarizes the problem e.g. TRIGG, START, STOP signals. Have you been able to successfully use multi-cycle averaging with any measurement frequency?

    Regards,

    Gabriel

  • 0 in reply to Gabriel Lake1
    Prodigy 150 points

    Thank you for your answer.
    For example, the settings for averaging 4 times are as shown in the figure below.

    With this setting, the trigger pulse is generated only once.

    Ch1 in the figure below is a trigger. ch2 is the start pulse.
    The start pulse is input 4 times every 2usec. If set the rate to less than 2usec, [measurement incomplete] will occur.
    Trigger is one time not 4times.

    Is there a mistake in the register settings?

    regards

  • 0 in reply to user5989766
    TI__Expert 3450 points

    Try setting the CALIBRATION 2 PERIODS down to 2 periods instead of 10. Using an 8MHz clock, calibration 2 is taking up 1.25us. I would also recommend using a 16MHz clock if possible. To use an external clock, change JP2 on the EVM and the GUI setting in the 'steup' tab. (see user's guide)

    Also, with 4 pulses in this configuration, you can expect 2 measurements to be taken, the one between the first pulse pair and another between the second pulse pair. I.E. 2 TRIGG pulses. Do you see this expected result if you increase the period of the start/stop pulses?

    Let me know if this helps, and if not, I will try to replicate this behavior with an EVM by the end of day tomorrow. 

    Regards,

    Gabriel

  • 0 in reply to Gabriel Lake1
    Prodigy 150 points

    Thank you for your answer.
    In the case of an 8MHz clock, it takes 125nsec * 10 = 1.25usec to calibrate.

    On the other hand, it remains questionable that the multi-cycle averaging trigger pulse occurs only once, regardless of the average number of times.

    It will not operate unless the average number of start and stop pulses are input for one trigger. For example, if you average 4 times, you have to input 4 start and stop pulses to one trigger.

    The data sheet diagram shows that as many trigger pulses as the average number of times occur.

    However, even with a 4-time average, the 4-time trigger does not occur.

    Please check the operation of the average and explain it.

    regards

  • 0 in reply to user5989766
    Prodigy 150 points

    I have more questions to ask.
    Comparing the variation in the measurement results when not averaging and the variation in the measurement results when averaging 128 times, for example, I feel that the effect is not so great.

    If you average 128 times, the variation should be reduced to (1 / root128), but the actual measurement is only about 1/2.

    The results of 16 times and 128 times on average are not so different.
    Where is the problem?

    regard

  • 0 in reply to user5989766
    Prodigy 150 points

    measure result

    on no average deviation=0.05675nsec

    SELECT DEVICE: TDC7201
    SELECT TDCx: TDC1
    TDC GRAPH SELECT: TDC2 - TDC1
    Start_to_Stop1  Start_to_Stop2  Start_to_Stop3   Start_to_Stop4  Start_to_Stop5  Delta_TOF  Delta_TOF DEV
    195.9619 195.9619 195.9619 195.9619 195.9619 0.064064 0.05675
    196.0259 196.0259 196.0259 196.0259 196.0259 0.064064 0.053103
    195.9988 195.9988 195.9988 195.9988 195.9988 0.005436
    196.0519 196.0519 196.0519 196.0519 196.0519 0.053103 0.084137
    196.0624 196.0624 196.0624 196.0624 196.0624 0.081377
    196.0678 196.0678 196.0678 196.0678 196.0678 0.005436 -0.13823
    196.0306 196.0306 196.0306 196.0306 196.0306 0.064216
    196.1147 196.1147 196.1147 196.1147 196.1147 0.084137 0.071683
    196.0306 196.0306 196.0306 196.0306 196.0306 0.024427
    196.1119 196.1119 196.1119 196.1119 196.1119 0.081377 0.049826
    196.206 196.206 196.206 196.206 196.206 0.060431
    196.0678 196.0678 196.0678 196.0678 196.0678 -0.13823 -0.00452
    195.9827 195.9827 195.9827 195.9827 195.9827 -0.02822
    196.0469 196.0469 196.0469 196.0469 196.0469 0.064216 0.047878
    195.9697 195.9697 195.9697 195.9697 195.9697 0.085057
    196.0414 196.0414 196.0414 196.0414 196.0414 0.071683 0.043936
    195.9988 195.9988 195.9988 195.9988 195.9988 0.111225
    196.0232 196.0232 196.0232 196.0232 196.0232 0.024427 0.053844
    196.0412 196.0412 196.0412 196.0412 196.0412 0.055844
    196.091 196.091 196.091 196.091 196.091 0.049826 0.087023
    196.0306 196.0306 196.0306 196.0306 196.0306 0.064092
    196.091 196.091 196.091 196.091 196.091 0.060431 0.140264
    196.02 196.02 196.02 196.02 196.02 -0.02846
    196.0154 196.0154 196.0154 196.0154 196.0154 -0.00452 0.03438
    196.0596 196.0596 196.0596 196.0596 196.0596 0.097872
    196.0314 196.0314 196.0314 196.0314 196.0314 -0.02822 0.071447
    196.0172 196.0172 196.0172 196.0172 196.0172 -0.02823
    196.0651 196.0651 196.0651 196.0651 196.0651 0.047878 0.026803
    195.9932 195.9932 195.9932 195.9932 195.9932 0.052823
    196.0783 196.0783 196.0783 196.0783 196.0783 0.085057 0.177124
    196.1182 196.1182 196.1182 196.1182 196.1182 0.113632
    196.1622 196.1622 196.1622 196.1622 196.1622 0.043936 0.042479
    195.9776 195.9776 195.9776 195.9776 195.9776 0.063314

    128 average deviation=0.02567nsec-  ----Isn't it too big?

    SELECT DEVICE: TDC7201
    SELECT TDCx: TDC2
    TDC GRAPH SELECT: TDC2 - TDC1
    Start_to_Stop1  Start_to_Stop2  Start_to_Stop3   Start_to_Stop4  Start_to_Stop5  Delta_TOF  Delta_TOF DEV
    196.1607 196.1607 196.1607 196.1607 196.1607 -0.024465 0.02567
    196.1363 196.1363 196.1363 196.1363 196.1363 -0.02447 -0.084781
    196.1713 196.1713 196.1713 196.1713 196.1713 -0.024205
    196.0866 196.0866 196.0866 196.0866 196.0866 -0.08478 -0.084781
    196.1395 196.1395 196.1395 196.1395 196.1395 -0.098298
    196.1153 196.1153 196.1153 196.1153 196.1153 -0.02421 -0.116383
    196.1713 196.1713 196.1713 196.1713 196.1713 -0.058479
    196.0866 196.0866 196.0866 196.0866 196.0866 -0.08478 -0.045184
    196.1926 196.1926 196.1926 196.1926 196.1926 -0.056204
    196.0943 196.0943 196.0943 196.0943 196.0943 -0.0983 -0.105624
    196.182 196.182 196.182 196.182 196.182 -0.077049
    196.0656 196.0656 196.0656 196.0656 196.0656 -0.11638 -0.034826
    196.1423 196.1423 196.1423 196.1423 196.1423 -0.034695
    196.0838 196.0838 196.0838 196.0838 196.0838 -0.05848 -0.045448
    196.1395 196.1395 196.1395 196.1395 196.1395 -0.067097
    196.0943 196.0943 196.0943 196.0943 196.0943 -0.04518 -0.055671
    196.182 196.182 196.182 196.182 196.182 -0.055804
    196.1258 196.1258 196.1258 196.1258 196.1258 -0.0562 -0.016614
    196.1607 196.1607 196.1607 196.1607 196.1607 -0.016747
    196.0551 196.0551 196.0551 196.0551 196.0551 -0.10562 -0.055671
    196.1713 196.1713 196.1713 196.1713 196.1713 -0.076913
    196.0943 196.0943 196.0943 196.0943 196.0943 -0.07705 -0.013715
    196.1501 196.1501 196.1501 196.1501 196.1501 -0.016522
    196.1153 196.1153 196.1153 196.1153 196.1153 -0.03483 -0.024465
    196.1395 196.1395 196.1395 196.1395 196.1395 -0.016126
    196.1048 196.1048 196.1048 196.1048 196.1048 -0.0347 -0.013843
    196.1607 196.1607 196.1607 196.1607 196.1607 -0.04558
    196.1153 196.1153 196.1153 196.1153 196.1153 -0.04545 -0.066158
    196.2138 196.2138 196.2138 196.2138 196.2138 -0.066426
    196.1467 196.1467 196.1467 196.1467 196.1467 -0.0671 -0.095137
    196.1395 196.1395 196.1395 196.1395 196.1395 -0.058342
    196.0838 196.0838 196.0838 196.0838 196.0838 -0.05567 -0.034957
    196.1501 196.1501 196.1501 196.1501 196.1501 -0.095608
  • 0 in reply to user5989766
    TI__Expert 3450 points

    Please provide a diagram or detailed explanation of your test setup here. 

    For your further questions, please repost them in a new thread.

    Thanks & Regards,

    Gabriel

  • 0 in reply to user5989766
    Prodigy 150 points

    Hello

    Please tell me the average algorithm.
    Which of the following?

    Add all and divide at the end.    (Simple average)
    (data 1 + data 2 + data 3 +_ _ _ _ _ _ _ _+ data n) / n = average n

    Average with previous data each time new data arrives.   (Moving average)
    (((data 1 + data 2) / 2 + data 3) / 2 + data 4)_ _ _ _ _ _ _ _+ data n) / 2 = average n

    regard

  • 0 in reply to user5989766
    TI__Expert 3450 points

    Thank you for posting your question in a new thread. I will close this one. 

    Regards,

    Gabriel