TUSS4470: Struggling to receive echo using 300kHz transducer

Hi Nick,

First, do you have the correct values on CINN and CFLT?  The calculation is based on the frequency of the transducer and can be found below.

Hi Eddie,

Thanks for the information.

We are using a 14nf & 2.2nf respectively and a bandpass set to 0x25.  Using 4 or 8 pulses makes no difference.

Can you provide any more guidance?

Kind Regards

Nick

Sure, can you provide some more information about your setup?  

How far away do you have the target placed when you are seeing no echo?

What is the target?  For initial test purposes, I suggest a large hard surface around 6-10inches away.

What is the medium?  Is it air?

Can you provide your full register configuration?  

Can you also provide scope shots on the transducer and VOUT pin?

A picture of the setup could also be helpful.

Hi Eddie,

Great thanks for this, answers below:

How far away do you have the target placed when you are seeing no echo? NP: Any distance

What is the target?  For initial test purposes, I suggest a large hard surface around 6-10inches away.  NP: A desk is the target with our operational target distance is 30mm - 150mm.

What is the medium?  Is it air?  NP: Yes thats correct, air.

Can you provide your full register configuration?  NP: BPF_CONFIG_1_REG 0x25 // Mode
BPF_CONFIG_2_REG 0x00 // Bandpass filter settings
DEV_CTRL_1_REG 0xBF // Log-amp configuration
DEV_CTRL_2_REG 0x00 // Log-amp configuration
DEV_CTRL_3_REG 0x01/0x00 // Device Configuration
VDRV_CTRL_REG 0x53 // VDRV Regulator Control
ECHO_INT_CONFIG_REG 0x17 // Echo Interrupt Control
ZC_CONFIG_REG 0x14 // Crossing configuration
BURST_PULSE_REG 0x04 // Burst pulse configuration
TOF_CONFIG_REG 0x01/0x02 // Time of Flight configuration

Can you also provide scope shots on the transducer and VOUT pin? NP: Sure we will get this over to you later.

Many thanks

Nick 

Nick,

Thanks for the details.  The configuration looks okay.  One thing to note in a monostatic(single transducer) configuration, is that at 30mm to 150mm, you will have significant ringing during the echo oversaturating the input, so no echo is seen, especially at the lower ranges.  To overcome this ringing, you can switch to a bi static configuration(1TX transducer and 1 RX transducer).  Another option that can help reduce ringing in a single transducer configuration is to place a dampening resistor(few hundred ohms or so) across the transducer.  This will reduce range, but ringdown will also be faster.  At 30mm, I don't expect a dampening resistor to be enough and would suggest a bi static configuration. 

With the above stated, you should be able to see an echo in the larger end of your range(150mm).  I will analyze your shots once you are able to send them as well.  Thanks!     

Hi Eddie,

Thanks for the previous help which solved our issue.  

We are getting echo's back now (see screenshot) and wanted to ask if you have any algorithms to help determine the signals embedded in the echo while the transducer is still ringing within the first ms?  

Thanks again.

Nick