• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 2 answers
  • Subscribers 79 subscribers
  • Views 291 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

MSP430FR5043: Ultrasonic Library: 32.768khz Crystal Requirement?

Jamal Bouajjaj
Prodigy 40 points
Part Number: MSP430FR5043


Hello,

Regarding the ultrasonic library provided, I noticed there is a "requirement" for a 32.768khz clock. Can this clock be omitted from a design? The only thing it looks like it's used for is for

"Used as background timer, to generate USS crystal/resonator settling times and to enable transitions to LPM3 during low power captures." as per https://software-dl.ti.com/msp430/msp430_public_sw/mcu/msp430/USSSWLib/USSSWLibWater/latest/exports/USSLib_02_40_00_00/docs/LibUsersGuide/markdown/CodeExamples.html?highlight=timer

Can't the internal VLO or LFMODCLK be used for Timer A1 instead with the compromise of settling time accuracy and power draw?

Please let me know if there are any internal usages of the LFXCLK and if there are critical to an ultrasonic application?

Thanks,

  • 0
    TI__Mastermind 29716 points

    Hi Jamal,

    LFMODCLK have about 24uA power consumption, and VLOCLK don't have a good accuracy.

    Thus we need a low power clock for the below function:

    • We use this clock to monitor HSPLL, if HSPLL frequency out of range, Error will occur.
    • We need an accurate measurement period for flow volume calculations.

    Thanks!

    Best Regards

    Johnson

  • 0 in reply to Johnson He
    Prodigy 40 points

    If power consumption is not an issue in a design (which in my case isn't), I have two follow up questions:

    - Why would HSPLL go out of it's frequency range if it's powered by a crystal?

    - Why can't HFTX be divided by 32 and have that clock the flow rate timer thru ACLK, if HFTX is powered by the USSXT_BOUT's output

  • 0 in reply to Jamal Bouajjaj
    TI__Mastermind 29716 points

    Hi Jamal,

    HSPLL is a 68MHz ~ 80MHz clcok, source by USSXT(4MHz or 8MHz).

    But if there are some issue for USSXT, like frequency instability, this will affect the metering accuracy, thus we are monitor this frequency by ACLK(32768Hz)

     

    USSXT and HFXT can't as the source clock for ACLK.

    Thanks!

    Best Regards

    Johnson

**Attention** This is a public forum