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PGA460: PGA460 sonar sensor questions

Tim Cruise
Intellectual 947 points
Part Number: PGA460
Other Parts Discussed in Thread: , ENERGIA

Hello TI Engineers and Experts,

I am interested in using PGA460 or PGA460-Q1 for automotives and vehicles applications.  Here are my questions:

  1. Is there hardware "Fast Fourier Transformation" implemented inside PGA460 and PGA460-Q1?
  2. How fast are PGA460 or PGA460-Q1 when measuring distance in the order of 10 metres between 2 vehicles?

Yours faithfully,

Timmy

  • 0
    TI__Mastermind 23045 points

    Hello Timmy,

    Thanks for posting to the sensing forum!  Thanks for some background in what you are trying to apply the sensor towards.

    1. I am not able to provide much info on that because we start getting into proprietary information of the DSP block. What I can say is that the device does implement the band-pass filter by using a second-order Butterworth IIR type filter, and the LPF is realized as a first-order IIR type filter. Are you trying to use the the PGA460 to implement an FFT some data or of the ultrasonic return info?

    2. The amount of time it takes for the device to measure 10 meters is mainly dependent on the speed of sound of the environment, but assuming we are using the speed of sound at room temperature which is 343 m/s, the time of flight of a 10m measurement can be calculated using the following formula: ToF = (2*distance)/(speed of sound).

    In this case it would be ToF = (2* 10m)/(343m/s) so the ToF =58.3ms.

    Now for the PGA460 in specific, it mainly depends on your device settings and communication protocol. Using the 10m at speed of sound at room temp example, we know that the ToF is a minimum of 58.3ms but the PGA460 allows you to configure the length of the ADC record period by using the P1_REC or P2_REC (different presets) so the record time will need to be longer than the max expected ToF. So, once the device is commanded to make a measurement the user must wait the entire record length, plus an additional 3.3us before attempting to read results from the UMR command 5. The MCU must still read the data from the device which can take some time depending on the method of communication used and the rate.

    Assuming P1_REC = 0x14, 61.44ms(record length) + 3.3us (dsp) + register read time ~= 65ms

    I dont know what the register read time would be so I just gave it a couple of milliseconds.

    Best,

    Isaac

  • 0 in reply to Isaac Lara
    Intellectual 947 points

    Hello Isaac,

    1. I am planning to use PGA460 as sonar circuit only.  Hardware accelerated FFT makes me feel more confident on it.  After all, it is an application about vehicle safety.  Faster response is better.  3.3us DSP should be very enough.
    2. If we use PGA460 to detect and measure vehicles and automotives distances continuously, how much power does it consume?
    3. My design is to read PGA460 sonar reading through a MCU and then feed the reading to a Bluetooth UART which in turn transmits to its vehicle host's dashboard.  Can you recommend a Simplelink MCU with built-in BLE which can controls a PGA460?
  • 0 in reply to Tim Cruise
    TI__Mastermind 23045 points

    Hello Timmy,

    1. One of the benefits of using IIR filters vs FIR is the processing speed in which they are able to be processed. But I am glad to hear that the 3.3us should be enough for your application.
    2. The average power consumed is dependent on a couple of factors, pulses, drive current, voltage, frequency. If you have an idea of what parameters you might use then you can actually enter them into the PGA460 GUI where we have a power budget calculator to obtain the average power consumed. Here is an FAQ on where to find this calculator and how to use it: https://e2e.ti.com/support/sensors-group/sensors/f/sensors-forum/1010405/faq-power-budget-calculator-how-to-calculate-power-consumption-for-pga460-and-tuss44x0
    3. As far as the MCU goes, unfortunately since I do not service the MCU's directly I am not too familiar with all of the offerings we have. It would be best to make a separate post regarding the MCU specifically along with other requirements you have for the MCU so that an engineer can make a recommendation based on all your requirements.

    I hope this helps, let me know if you have other questions I can help out with!

    Best,

    Isaac

  • 0 in reply to Isaac Lara
    Intellectual 947 points

    Isaac,

    ok. I've found the software estimating its power consumption.

    As to the software of PGA460, is it supported primarily through Energia?  Is there any software support of PGA460 in TI Code Composer Studio?

  • 0 in reply to Tim Cruise
    TI__Mastermind 23045 points

    Hey Timmy,

    Glad you were able to find the power calculator!

    That is correct, the only example code we have available for the PGA460 is through Energia, nothing for Code Composer Studio (CCS) at this time. Although, you can important an Energia sketch to CCS, this will allow you to see a low-level debug/breakdown of the C-Programming equivalent that runs in the background.

    As far as I know, what you import wont run on CCS but you could always repurpose the code for the MCU that you do end up choosing.

    Best,

    Isaac