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BOOSTXL-TUSS4470: Cant seem to find the ECHO signal (and alot of noise on transducer pin)

Jarmo Dekkers
Prodigy 10 points
Part Number: BOOSTXL-TUSS4470

Tool/software:

Hello, I'm trying to find the captured ECHO signal on my oscilloscope, but I can't seem to point out the ECHO in the signal. I know the transducer (I'm using it in monostatic configuration) is bursting, because I can see it on my oscilloscope, and is listing because I can see it from the status bits. I used the speed of sound calculation to pinpoint the time the ECHO needs to return for an object that is 1 meter away. Time = distance /speed = 1 / 340 = 2941 us, this time can be seen on figure 3. So, any advice on how I can see the returned ECHO?

And I also get a lot of noise on the transducer pin that I can't get rid of. Is there a way to reduce the noise?

I send 16 pulses with 40 kHz frequency to the BOOSTXL-TUSS4470 module (see figure 1) and it is in IO_MODE 1.

And these are the register values:

BPF_CONFIG_1=0x00

BPF_CONFIG_2=0x00

DEV_CTRL_1=0x00

DEV_CTRL_2=0x05

DEV_CTRL_3=0x01

VDRV_CTRL=0x00

ECHO_INT_CONFIG=0x00

ZC_CONFIG=0x00

BURST_PULSE=0x10

TOF_CONFIG=0x00

Here the 16 pulses are seen on the + terminal of the transducer.

Here the noise can be seen, on the + terminal of the transducer.

Around this time, the returned ECHO needs to be seen according to the calculation.

Best regards,

Jarmo

  • 0
    TI__Mastermind 40400 points

    Hello Jarmo,

    There is a good video below discussing the GUI and configuration for use with the 40kHz transducer included in the EVM kit.  The video can be found at the bottom of the page.

    https://e2e.ti.com/support/sensors-group/sensors/f/sensors-forum/748143/faq-ultrasonic-sensors 

    What type of object are you sensing?  For initial testing, start with a large hard surface for the best reflection.  Also, try bringing the object closer to the transducer to test if any echo is seen at shorter range.  

  • 0 in reply to Eddie LaCost
    Prodigy 10 points

    Hey Eddie,

    Thanks for the response, I forgot to say in my post that I didn't buy the kit but only the BOOSTXL-TUSS4470 evaluation board. I am using an Arduino as microcontroller.

    For the test, I am trying to sense a glass wall in my office. I will try to put the transducer closer to the wall to see if I can spot the echo.

  • 0 in reply to Jarmo Dekkers
    Prodigy 10 points

    Hey Eddie,

    I have moved the transducer closer to the wall, 50 cm instead of 100 cm, and this is the scope image I get. Blue line being the VOUT pin and yellow is the + terminal of the transducer. The second vertical white dotted line is the moment the transducer should receive the echo. I also placed a 100 Ohm resistor parallel to the transducer to reduce the ringing.

  • 0 in reply to Jarmo Dekkers
    TI__Mastermind 40400 points

    Thanks.  It does look like there is a weak echo at the second marker.  Can you provide your schematic?  

  • 0 in reply to Eddie LaCost
    Prodigy 10 points

    Hi,

    Sorry for the late response, but I don't have a schematic because the evaluation board is directly connected to the Arduino Uno. But these are the connections:

    BOOSTXL-TUSS4470 / Arduino Uno

    SCLK / Digital pin 13

    MISO / Digital pin 12

    MOSI / Digital pin 11

    NCS / Digital pin 10

    IO2 / Digital pin 9

    IO1 / Digital pin 2

    And I will test again, to see if there is indeed a weak echo at the second marker. 

    UPDATE:

    I tested again with an object 30cm away from the transducer and I changed some register values in DEV_CTRL_1 and 2 to strengthen the VOUT signal, and indeed I can see the returned echo.

    Thanks Eddie for helping me out.

    Best regards,

    Jarmo

  • 0 in reply to Jarmo Dekkers
    TI__Mastermind 40400 points

    Jarmo,

    Glad to see that you are able to capture some echo now.  For longer range, you may also want to change the 100 ohm paralllel resistor or remove it completely as this will dampen the signal.