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Original question:

EVM430-FR6043: How to use w/ 40kHz transducers....

EVM430-FR6047: Single Transducer Setup

Sahaj Walia
Prodigy 130 points
Part Number: EVM430-FR6047
Other Parts Discussed in Thread: TDC1000

Hi,

I was attempting to use this dev board to test the accuracy of the MSP430 using just a single 1MHz transducer to get the absolute TOF. I have tried hooking up the transducer to CH1 and then grounding CH2 but that did not seem to work. If anyone has some guidance that would be greatly appreciated.

  • 0
    TI__Guru 71216 points

    Hi Sahaj,

    Can you tell me a little more about your setup?  Is the transducer in water and you are using the signal reflection??

    Are you using the USS GUI to setup the initial parameters?

  • 0 in reply to Dennis Lehman
    Prodigy 130 points

    Hi Dennis,

    The 1 MHz Transducer is mounted to the outside of the bottle(SMD20T21F1000R) and I have it hooked up to CH1 as shown to the left. I am attempting to use the reflection pulse to measure the Absolute TOF. I am using the USS GUI to setup the initial
    parameters and have included my settings as well. Unfortunately I am not getting any ADC reading or anything on the waveform graphs. NOTE: Although there are multiple transducers mounted to the bottle I am currently using the one mentioned 

  • 0 in reply to Sahaj Walia
    TI__Guru 71216 points

    Hi Sahaj,

    Not sure what attenuation properties the bottle material might have on the ultrasound, but keep that in mind.

    What value to you have for "Gap between pulse start and ADC capture"?  This is located on the Parameters tab.  Can you provide a screen shot of that tab?

    Looking at your photo, I'm guessing the bottle size is ~8cm across.  Doing some quick math, at room temp the speed of the ultrasound is 6.75us per cm so the time for the primary wave to cross the bottle would be about 54us.  The reflected pulses would take another 54 on the return, so a total of 108us.

    You need to set the Gap parameter to something just a little sooner than this to capture the beginning of the ADC properly, so try a Gap = 100us.  Once you see the ADC waveform you may have to adjust a couple of us in either direction.

    Also, what is your the gain setting for the PGA.  You will find this on the Parameter tab.  You may have to try a few different values until you get an ADC waveform that is ~ +/- 800 to 900 counts.

  • 0 in reply to Dennis Lehman
    Prodigy 130 points

    Hi Dennis, your assumption was correct the bottle is about 8cm across. I have adjusted the Gap to 100 us but I am receiving an error "no signal detected in upstream and downstream channel". I have included screenshots of my parameter tab, ADC Capture, and Error tab. I can verify that the transducers do work as I have a TDC1000 Evaluation board and could see an accurate TOF using the same bottle setup.

  • 0 in reply to Sahaj Walia
    TI__Guru 71216 points

    Hi Sahaj,

    If you have an oscilloscope, or logic probe that supports analog measurements, can you get a shot of CH0_OUT and CH0_IN?

  • 0 in reply to Sahaj Walia
    TI__Guru 71216 points

    Hi Sahaj,

    Looks good on the transmit side, but what about on the receive signal on CH0_IN?  Can you capture that as well?

  • 0 in reply to Dennis Lehman
    Prodigy 130 points

     I was taking another look at my ADC capture and saw this but there is a repeating error for "No Signal Detected Upstream"

  • +1 in reply to Sahaj Walia
    TI__Guru 71216 points

    Hi Sahaj,

    Great! We are making progress.

    The signal will be quite small, so your logic probe does not see it, but you do have a good capture of CH1 in the GUI.  BTW, you will need some more gain to get a larger signal (~ +/-800 counts) and adjust the Gap parameter to something < 100us so you see the entire waveform.  Here is example;

    Also, check our TI Academy for Ultrasonic Water Flow meter design and test.  It has all the steps to help get your signal optimal for absTOF measurements.

    Now for the upstream error I suspect what is happening is you are using the default water demo code, which is expecting both upstream and downstream signals.  But you are only using one transducer so this is why it complains about not seeing upstream.

    Open up the USS_userConfig.h file (located in the USS_Config folder in your CCS project) and edit as shown here by changing the USS_SEQUENCE_SELECTION.  Choose the channel you have your transducer connected up to.

    Let me know how this works.

  • +1 in reply to Dennis Lehman
    Prodigy 130 points

    Hi Dennis,

    Looks like we are getting closer, I adjusted the parameters within the GUI like you said and can see a clear ADC Capture, I am having trouble importing the USS example project into CSS, I have followed the Guide indicated in:

    https://software-dl.ti.com/msp430/msp430_public_sw/mcu/msp430/USSSWLib/USSSWLibWater/02_40_00_00/exports/USSLib_02_40_00_00/docs/LibUsersGuide/markdown/CodeExamples.html#modify

    and am unable to build the project/run

  • 0 in reply to Dennis Lehman
    Prodigy 130 points

    Update: I was able to build and flash the board with the updated settings from CSS but there is still an issue with the DNS channel providing no signal and unable to plot waveforms

  • +1 in reply to Sahaj Walia
    TI__Guru 71216 points

    Hi Sahaj,

    Ok, let me try on my side and see what might be the issue.

  • 0 in reply to Dennis Lehman
    Prodigy 130 points

    Hi Dennis,

    I was able to get everything working after your previous suggestion, the issue was that I was opening the project rather than importing it, I have been successfully able to get an ADC reading and TOF now. Thank you for all of your help.

  • 0 in reply to Sahaj Walia
    TI__Guru 71216 points

    Hi Sahaj,

    Excellent! Glad to hear you can move forward.

    BTW, I have to go back and correct my instructions to modify the code to use the single channel.  One of my colleagues indicated you don't need to change the Water Demo code.  Just short CH0_IN to CH1_IN and CH0_OUT to CH1_OUT.

    With that note, I'll close out this posting.

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