Analyzing Texas Instruments DSP Power Consumption

Why Monitor Power Consumption?

In order to effectively develop low-power devices for DSPs, it is important to understand not only the lowest possible power for a DSP at run-time, but also to understand how much power is consumed when the DSP is running different peripherals and algorithms or while it is in sleep mode. As a result, DSP design engineers need to understand power drains on their products while emulating the behavior of the DSP when embedded in the real-world.

Until now, understanding the exact power consumed by a DSP during any given process has been difficult to quantify and measure. The Power Measurement bundle, a joint effort between Texas Instruments, Spectrum Digital and National Instruments, gives you the ability to understand the various power needs of DSP-based devices. This bundle uses a data acquisition device from National Instruments to measure the power being consumed by the DSP core and I/O. The bundle includes turnkey software built using NI LabVIEW (NOTE: software is a LabVIEW-built executable, it DOES NOT require the user to have LabVIEW installed on the PC), NI data acquisition (DAQ) hardware (PCI-6014E), Spectrum Digital EVM320VC5509A DSP evaluation board (EVM), and necessary cables. After installing the PCI DAQ device to your PC, cable the DAQ board to the DSP evaluation board, and use the software utility to measure core and I/O power of the DSP device. Also you can perform basic analysis on the power measurement data such as max/min values, average power consumed overtime, or save the data for off-line analysis.

Using National Instruments data acquisition hardware and your PC allows you to use low-cost hardware that is programmable through software. This application note will discuss the functionality and benefits of this bundle.

Virtual Instrumentation for DSP Developers

Virtual instrumentation is a revolutionary approach to test and measurement, pioneered by National Instruments. With virtual instrumentation, engineers use software to define the functionality of modular hardware, such as the data acquisition device provided in the Power Measurement Bundle, to quickly create user-defined measurement devices. Through a flexible software environment, the user-defined measurement system delivers data acquisition, analysis, and data presentation that exactly match the needs of your device under test. The Power Measurement Bundle is built on the concept of virtual instrumentation, allowing you to extend the functionality of your PC and transform it into a power measurement and analysis tool for DSP designs.

The majority of DAQ applications (including this one) use driver software to connect the development environment (LabVIEW) to the DAQ hardware. Driver software is the layer of software that directly programs the registers of the DAQ hardware, managing its operation and its integration with the computer resources, such as processor interrupts, DMA, and memory. Driver software hides the low-level, complicated details of hardware programming, providing the user with an easy-to-understand interface or a stand-alone application program. The Power Measurement Bundle was created using LabVIEW and NI-DAQmx driver software to build the stand-alone power measurement executable. Because plug-in DAQ devices do not have displays attached directly to the hardware like traditional scopes or multi-meters, the software is the only interface you have to the system. The software is the component that relays all the information about the system, and it is the element that controls the system. The software integrates the transducers, signal conditioning, DAQ hardware, and analysis hardware into a complete, functional DAQ system.

The key component to a virtual instrumentation system is an integrated software framework that delivers a modular structure for building high-performance, automated measurement and control systems. For maximum performance, ease of development, and system level coordination, the components of the framework must be independent, yet tightly integrated. This modular, integrated structure empowers developers to rapidly build measurement systems and modify them easily as the system requirements change. Developing a measurement and automation system with a tightly integrated software framework delivers numerous benefits, including:
· Significantly increased productivity throughout the development, deployment, maintenance, and modification process with rapid application development tools designed for measurement and control applications
· Higher performance measurement and automation systems, as the tools at each level are designed to work well together to deliver maximum system performance
· More tightly integrated systems that bring together numerous diverse measurement devices into high-level systems that connect easily to other processes throughout the organization
· Decreased costs throughout the product life cycle

The Measurement and Control Services Software plays a critical role in delivering the key benefits of a modular computer and networked-based measurement system. The components of this software -- flexible high-level application programming interfaces (APIs), integrated driver engines and a configuration manager -- must all integrate within an application development environment (ADEs), such as LabVIEW, to attain maximum system performance and development productivity. The specific tasks of the Measurement and Control Services Software include integration of measurement devices, as well as local and distributed configuration and programming of the measurement devices. For more information regarding the Measurement and Automation Software frame work, read the Increase Productivity with an Integrated Software Framework for Measurement and Automation white paper.

You can extend the functionality of the Power Measurement application included with this bundle by using the LabVIEW development environment to integrate other aspects of your power measurement system. For instance, you can extend your testing system to integrate the video or audio signals for peripherals, or you can integrate TI Code Composer Studio (CCStudio) automation to develop testing sequences for different DSP algorithms. With the tightly integrated framework of LabVIEW and National Instruments hardware, you can quickly build systems that function exactly as you need them to.

Reducing Time to First Measurement

The Power Measurement Bundle has been streamlined to reduce the time it takes to get to your first measurement. First, the Spectrum Digital EVM device has built-in signal conditioning for direct connectivity to a NI SC6850 cable. Simply connect the cable to the EVM board and the software will immediately begin measuring the power directly from the core and I/O of the DSP. Second, you are provided with turnkey software written with NI LabVIEW. This turnkey software executable does not require LabVIEW or LabVIEW programming knowledge. However, you can customize the operation of the Power Measurement tool using LabVIEW graphical development and the included LabVIEW source code that was used to build the turnkey executable. The bundle will include step by step instructions for configuring your DAQ device and taking measurements.

When customizing the application using LabVIEW, you continue to have a short time to first measurement by using configuration-based Express technologies in LabVIEW, such as the NI DAQ Assistant. The DAQ Assistant, which is included with NI-DAQ 7, provides a graphical, interactive guide to configuring, testing, and acquiring measurement data. With a single click, you can even generate code based on your configuration, making it easier and faster to develop complex operations; and because DAQ Assistant is completely menu-driven, you will encounter fewer errors and drastically decrease the time to your first measurement.

Moving Beyond the Power Measurement Tool

You can expand and customize your DSP power monitoring system using LabVIEW. You can use the LabVIEW DSP Test Integration Toolkit to set power levels within the DSP through RTDX, modify characteristics and parameters on algorithms, or even dictate which algorithm is executing on your DSP. For more information on using LabVIEW to debug and test your DSP products, visit www.ni.com/dsp.

Conclusion

Using the Power Monitoring Bundle, you can quickly acquire and analyze power consumption data from your DSP designs. This bundle not only provides fast time to first measurement, it is also easily extensible through LabVIEW graphical programming.

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