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[FAQ] PGA460: Everything You Need to Know for Ultrasonic ToF (Air-Coupled) [Collateral, Tools, Designs]

Part Number: PGA460

Ultrasonic Time-of-Flight Measurements (through Air)

If your application requires the use of ultrasonic time-of-flight to measure distance through air from a few centimeters up to several meters, then the PGA460 ultrasonic sensor signal conditioner is TI's recommended device. All officially released collateral is available on the PGA460 product page (www.ti.com/.../PGA460). The following collateral will be available on E2E until officially released to the product page:

PGA460 E2E Discussions/Collateral:

PGA450 E2E Discussions/Collateral:

Getting Started and Evaluation Flow

Where do I begin?

To begin evaluation of the PGA460, purchase the PGA460-Q1 EVM, which contains all the necessary hardware required to evaluate a full-scale ultrasonic module equivalent with a master controller. Once the hardware is in hand, download and view the PGA460-Q1 EVM Quick Start Guide. The quick start guide provides the step-by-step procedure to setting up the EVM hardware and installing the PGA460-Q1 EVM GUI. In addition to the supporting documentation, the six part PGA460 EVM & GUI Video Series demonstrates how to setup, install, and run the evaluation tools. The basic device settings are introduced to start capturing return echoes within minutes of unboxing the EVM. For a detailed description of the EVM’s hardware and GUI, refer to the PGA460-Q1 Ultrasonic Signal Conditioner EVM with Transducer User's Guide.

After setting up the EVM, and verifying the GUI works, how do I tune my solution?

To tune an ultrasonic sensor solution, the user must understand the capabilities and limitations of the ultrasonic components. The PGA460-Q1 Ultrasonic Module Hardware and Software Optimization application note introduces a detailed description on how to determine which transducer, driver, and power combination should be used depending on the targeted objects and environmental operating conditions. Throughout your evaluation and component selection, refer to the PGA460-Q1 Frequently Asked Questions (FAQ) and EVM Troubleshooting Guide application note for advanced troubleshooting and debugging.

After tuning my solution on the EVM, how do I port the settings from the GUI and configure my custom solution?

The first step to porting your solution is to capture the optimized register map using the GUI. The GUI is able to save all user EEPROM settings, as well as the threshold times and levels stored in volatile memory. To save the register map using the GUI, navigate to the Memory Map tab. Before clicking the Save Grid icon, be sure to click the Read All icon to update the memory map page with the latest device settings. When the Save Grid icon is clicked, the user will be prompted to save the time stamped register map grid as a .txt file. This .txt file can be used as a reference or be loaded to other PGA460 devices using the GUI.

Since the EVM is not the optimal size for an ultrasonic module, the PGA460Q1SFF reference designs are available as examples to the small form factor (SFF) size for a PGA460 solution. Variants include a transformer driven, a half-bridge driven, and a full-bridge driven. Depending on the transducer and driver mode optimized on the EVM, select the appropriate reference design variant as a starting point for your customized hardware.

The SFF reference design routes the UART’s TXD and RXD pins and the IO pin to the five-pin connector on each variant. Typically either only the two UART pins or the single IO pin are routed the module connector for communication. Power and ground are always required, so the minimum number of pins per module is three.

The GUI primarily uses UART to evaluate the PGA460. However, SPI, TCI, and One-Wire UART can also be used to fully program and evaluate the PGA460. The GUI uses TI’s USB2ANY proprietary code to communicate from a PC to the PGA460 device. The GUI source code is not available to the public. Instead, the PGA460 Energia Library and Code Example and PGA460-Q1 Software Development Guide should be used as an example for master controller implementation and programming guidelines. The example runs on the Energia IDE when using any of the TI LaunchPad development kits, including the MSP-EXP430F5529LP base of the PGA460-Q1 EVM. Therefore, the PGA460-Q1 EVM can be used to run the GUI or Energia sketches. Modify the Energia sketch to meet the system requirements of the end solution.

How can I prepare for mass production programming and system integration?

If the system requires the PGA460 device’s user EEPROM settings to be burned prior to the ultrasonic module to being installed in the system, then a custom mass production tool must be designed to program the EEPROM module. The MSP-EXP430F5529LP from the PGA460-Q1 EVM can be used as the base of the mass production tool, and would only require the user to build a mass production BoosterPack for the custom PGA460 module form factor. The PGA460 Energia sketch can be modified such that the mass production tool performs a bulk EEPROM write and burn to multiple modules simultaneously or sequentially based on the PGA460 address assigned to each module. For instance, if all modules will have the same UART address for a star topology system (independent UART channel for each module from the master), then all modules can be programmed simultaneously. If each module requires a different UART address for a bus topology system (a single UART channel shared between each module), then the modules must be written to sequentially. The PGA460 UART address is ‘0’ by factory-default.

If the master controller within the system is able to perform the bulk EEPROM write and burn command, then a mass production tool is not necessary, and a blank module can be installed in the system. This approach is only recommended for a star topology because the PGA460 is not able to perform daisy-chain or automatic slave node position detection (SNPD). If a bus topology is required, then the modules must be pre-programmed, installed and programmed one at a time in the system, or use a the support of external switches and master control signals to achieve SNPD. See section 4.14 for an example implementation of SNPD on for PGA460 bus.

Refer to the PGA460 Frequently Asked Questions (FAQ) and EVM Troubleshooting Guide (http://www.ti.com/lit/pdf/slaa733) for additional details and discussion on ultrasonic time-of-flight development.

 

Akeem Whitehead // Texas Instruments // ASC-SENSING-SSC // Applications Engineer
Visit our Ultrasonic Sensing FAQ page for additional information.
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    Akeem Whitehead // Texas Instruments // ASC-SENSING-SSC // Applications Engineer
    Visit our Ultrasonic Sensing FAQ page for additional information.

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