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BOOSTXL-TUSS4470: Threshold value

Julia Mattos
Prodigy 40 points
Part Number: BOOSTXL-TUSS4470

Hello, 

How do I know which threshold value to use?
What parameters should I use to know the threshold value?

Thank you, 

Julia

  • +1
    TI__Mastermind 21430 points

    Hello Julia,

    Thanks for posting to the sensors forum! The threshold is dependent on your application, the threshold activates the OUT4 pin. This means that whenever a returned echo meets the programmed threshold value you will see a signal output on the OUT4 pin. This can be used as an interrupt to an MCU to perform some other function, wake up another system, or some users use this interrupt to calculate their ToF.

    In order to enable this function the ECHO_INT_CMP_EN bit must be set an the threshold is programmed in the ECHO_INT_THR_SEL, there is a formula on how to calculate what value would generate this interrupt so please check the datasheet to verify you are using the correct formula for your configuration. Both of these registers are in the ECHO_INT CONFIG register, or register 0x17.

    I hope this helps let me know if there are any other questions!

    Best,

    Isaac

  • +1 in reply to Isaac Lara
    Prodigy 40 points

    Thank you, that was very enlightening!

    One last question, for very short ToF like very small distances, for example 5-10 cm in the water, what would be the recommended threshold value?

  • +1 in reply to Julia Mattos
    TI__Mastermind 21430 points

    Hello Julia,

    Always glad to help out! For a short ToF around 5-10cm in water keep in mind we recommend using two devices for this type of solution. One device will generate the ultrasonic pulse while the other device is strictly just listening. If you try to use one device to generate and listen this will be very difficult because the input saturated for some time meaning it is not able to distinguish when it receives a return echo.

    I dont have a recommended threshold value because your VOUT level depends on various factors such as what voltage you are using to drive the transducer. What you can do is run a couple of measurements and check the VOUT pin to see what kind of output to expect based on your driving voltage. From there you can figure out what your threshold should be and calculate backwards based on what your system is producing.

    Best,

    Isaac