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PGA460-Q1: Help Required Driver Development and Evaluation

Part Number: PGA460-Q1
Other Parts Discussed in Thread: BOOSTXL-PGA460, PGA460,

Support Path: /Product/Development and troubleshooting/

I am working on evaluating TI PGA460 for my company, to be used in IoT Sensing application. I have BOOSTXL-PGA460 unfortunately I don't have MSP EXP430 to connect with. Upon reviewing schematics and datasheet I was able to communicate with PGA460. 

My current scenario is

PGA460 EVM connected with daughter card I tried with both Transformer Driven and Direct Drive. The scenario given below I used with both.

I connected my UARTRX with test point RXD and UART RX with test point TXD

I sent the following to configure the device 

550A201DB8 // set current limit to 250 mA

550A1E0EC9 // Set pulses to 14

550A1B4A90 // Set BPF_BW tp 4 Khz and GAIN_INIT to 64dB

550A213F95 // LPF_CO to 2 Khz

550A2912BA // Digital Gain to 4

550A22448F // Record Length to 20.48ms

550A2600CF // AFE_GAIN_RING to 58 to 90 dB

I also tried 

550A1C8E49

however it fails as when I read it by sending READ REGISTER COMMAND it returns

55091cda488c2b 

It is my understanding that it means invalid command (48) and the register value is still 8C

When I send 

550001FE // to do Burst and Listen and then send 5505 to read Ultrasonic Measurement Result it always returns 

5505403b0aa94b85

3B0A is always constant no matter if I bring it closer to an object or far away. I also checked Transducer Echo Data Dump and it is always the same.

I need help regarding what I am missing. I think it could be that I am not configuring it properly as I dont have the MSP 530 to verify. I also need to develop driver to integrate with our product so understanding how it works is necessary as well.

Best Regards

  • Hi Salman,

    The threshold must be written to at least once after start-up to clear the threshold CRC error that is always flagged high on initialization. The threshold CRC error must be cleared before the PGA460-Q1 is allowed to execute a Burst & Listen or Listen-Only command.

    To use the asynchronous UART mode, refer to the 7.5.1 UART and USART Communication Examples on page 55 of the PGA460-Q1 datasheet. Try replicating these commands using your master MCU. Be sure your master MCU is using the PGA460 required UART frame structure:
    •8 data bits
    •1 start bit
    •2 stop bit
    •No parity bit
    •No flow control
    •Interfield wait time (only required when using 1 stop bit)

    Note: Most MCU's default to 1 stop bit, so ensure you have configured your master's UART port for 2 stop bits.

    The PGA460 supports a baud rate between 2.4k-115.2kBaud. What baud rate are you using?

    What is the value of VPWR? The PGA460 requires 6-28V to operate correctly. A 5V USB based supply will not be sufficient enough to power the PGA460.

    A diagnostic field value of 0x48 indicates you transmitted an invalid checksum. For additional async UART examples, or to compute the checksum of any command sequence, refer to the GUI's Interface Mode --> UART page's command selection. Select the desired command from the drop-down with the appropriate UART Addr (0 by default), then click Run Command to see the raw serial sequence with appended checksum printed in Hex format on the UART terminal. You do not need to have the EVM connected in to use this feature of the GUI.

    To check if your UART port is correctly communicating with the PGA460, send a basic command, such as a register read command. Here is an example master transmit sequence in hex: {09 2B CB}
    where:
    •09 is the register read command and addr 0
    •2B is the register address to read EE_CRC (usually returns a non-zero value)
    •CB is the checksum for this transmit sequence
    The PGA460 should return three values when using this command:
    •Diagnostic field (0x40) if master transmit was successful
    •Register address value
    •PGA460 generated checksum

  • Hi Akeem Whitehead

    Thanks for the explanation. We were able to get some raw readings which are not accurate however I think that is a configuration problem. We are evaluating PGA460 for IoT application which requires sensing of 5cm to 150cm (we can adjust the configuration when we want to measure small distances and long distances). Do you think the minimum sensing distance of 5cm is possible with PGA460 and if not what is the minimum distance that can be measured. Can you recommend a Ultrasonic Transducer for short distance measurement. Also is the wired transducer that comes with the daughter board capable of measuring short distances.

    Best Regards

  • Hi Salman,

    The Murata MA58MF14-7N (twisted-wire transducer) on the EVM is only able to measure downwards of 10cm in mono-static mode, so this specific transducer configuration will not work for your application.

    The PGA460 can detect echoes as low as physically possible (not device limited, but transducer limited). If your range is 5cm to 150cm, I recommend the following options:
    1) Mono-static high-freq transducer (180-480kHz) in transformer driver mode
    2) Mono-static high-frequency transducer in a bridge driver mode
    3) Bi-static low-frequency transducer (40-80kHZ) in any driver mode

    The benefit of high-freq transducers is that they are designed to be more effective at measuring in the very short range (sub-10cm). Depending on the specific type of object (size, shape, surface material), you may be able to use a high-freq transducer with a bridge driver for long-ranging as well to eliminate the cost and size of the transformer. Low-freq transducers will always offer superior long range performance. Note: high-frequency transducer also have very focused beam patterns / field-of-views (sub-10deg).

    I recommend that you look into the Massa 200639-501 (Model E-188/220) high freq transducer in either bridge or transformer mode. You can use the EVM's half-bridge driver for evaluation. Otherwise, you will need to order a high-freq transformer.
    . High-freq transformer options include:
    1) TDK-EPCOS B78416A2386A003 transformer, contact TDK-EPCOS support at en.tdk.eu/.../product-inquiry
    2) Wurth Electronics 750316928, contact the Wurth Electronics Midcom Inc. Headquarters at midcom@we-online.com
    When contacting either of these companies, be sure to mention that you are developing an ultrasonic sensing solution using the TI PGA460.

    For a full-listing of high-frequency transducers and transformers, go to:
    e2e.ti.com/.../620399