FXTH87xx Measure Time Issue

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FXTH87xx Measure Time Issue

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waynelin
Contributor I

Hello

We use software to control I/O high and low to analyze conversion time is 24.5ms (detect pressure + others)

But in datasheet define (setting average = 16, should 8.6ms-0.8ms = 9.4ms)

We finding input power maybe cause this issue.

Use power supply : “normal” (9.4ms)

Use battery : “abnormal” (24.5ms)

As this test result  maybe i can say "software is correct" because same board same software never happen with power supply.

Could tell me why different between power supply and battery or what situation will cause this state.

Others I check MFO (I think maybe MFO cause detect time issue)

But TPMS_MFOCAL always return 255 in datasheet “255 is reserved as an error code for when the external XTAL is not present”

Best regards,

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david_diaz
NXP Employee
NXP Employee

Hello Wayne,

Once the device has been programmed, it is necessary to reset it after having disconnected the multilink from the device (even if the multilink has been disconnected from the computer). I assume this is one of the possible reasons of this issue.

If you do not follow the procedure mentioned, then, it will not behave in the usual way and time to leave STOP modes (after measurements for example) will be longer.

So when using a battery (or an external power supply) the following procedure must be the following:

  • Program the device
  • Disconnect the multilink from the device (not only from the computer)
  • Reset the device (remove and reconnect the J1 jumper)

In the other hand, the pressure measurement time is dependent on clock tolerances.

Can you please make a GPIO toggle periodically and then check with an oscilloscope if the period is the same when using the external power supply or the battery?

If the period is significantly not the same, can you please send me details on how they proceed, the results you get (period of the toggling in each case) and tell me what you do at the beginning of your main?

Which registers are accessed at the beginning of the main?

I hope this information will be useful for you.

If I misunderstood your question, feel free to let me know.  I will be glad to help.

Have a great day.

David Diaz.

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