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TDC7200: Wait time between start new measurement and start signal.

ANDREW DEMEDEIROS
Prodigy 80 points
Part Number: TDC7200

Hi,

I am evaluating the TDC7200 for a time measurement application, where there is an indeterminate amount of time between starting the measurement, and reception of the "START" input signal. I have looked through the datasheet, and I do not see any issues with this, but I wanted to ask here to be sure.

To clarify, operation would be as follows:

  • System is powered, MCU sets config registers in TDC7200
    • Starts new measurement on TDC7200
    • TDC7200 generates trigger signal
  • Wait some period of time START signal is generated
    • This could be multiple minutes as it is generated by an operator pushing a button
  • STOP signal received within 1ms of START signal

Could there be any issues with this approach?

Thank you,

Andrew

  • 0
    TI__Genius 13590 points

    Hi Andrew,

    Thank you for posting to the Sensing Forum.

    This isn't something that we have defined in the datasheet, but I will test this in the lab tomorrow and get back to you with the results.

    Best,

    ~Alicia

  • 0 in reply to Alicia Rosenberger
    Prodigy 80 points

    Hi Alicia,

    Thank you, I look forward to your results!

    Andrew

  • 0 in reply to ANDREW DEMEDEIROS
    TI__Genius 13590 points

    Hi Andrew,

    After testing this scenario in the lab, it looks like after starting a new measurement after the TRIGG pin goes high you can only wait a maximum of 300 ms for the START signal to get generated before the device gets timed out. 

    An alternative that I would suggest, would be to have the operator pushing a button be what generates the TRIGG signal and starts a new measurement on the device, which would in turn enable the START pin to receive the START signal, you can generate the START signal shortly after the button is pressed, similar to what is described in section 8.4.6 Measurement Sequence of the datasheet.

    Best,

    ~Alicia

  • 0 in reply to Alicia Rosenberger
    Prodigy 80 points

    Hi Alicia,

    Thanks for looking into this. I had run some tests yesterday and it seemed like this was possible. I will post my setup tomorrow to compare differences.

    Which register needs to be read to determine if the device has timed out?

    Unfortunately the operator action is a unconnected mechanical action which can't be tied into the circuit.

    Thanks,

    Andrew

  • +1 in reply to ANDREW DEMEDEIROS
    TI__Genius 13590 points

    Hi Andrew,

    If the tests that you conducted showed that it was possible, then it could be that it is. The tests that I ran involved using the TDC7200EVM GUI which could have had some kind of timeout function which caused the device to timeout after a period of time to prevent the code from potentially entering into an infinite while loop.

    Best,

    ~Alicia