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Earlier in this series, we touched on one problem that can arise when sampling an analog signal, namely the problem of aliasing. There are three other issues with signal sampling to which we now turn our attention: digitization effects, finite register length effects, and oversampling. So far, weve assumed that all of the signals were measuring are continuous analog values; i.e., our measurements are completely accurate. Even in the cases in which we have noise, the underlying assumption is that the measurement itself, for example the noisy sensor output voltage, is known precisely.

Although signal processing is usually associated with digital signal processors, it is becoming increasingly evident that FPGAs are taking over as the platform of choice in the implementation of high-performance, high-precision signal processing. For many such applications, the choice generally boils down to using either a single FPGA, a FPGA with an associated DSP processor or a farm of DSP processors.

The ARM Cortex™-M4 processor is the latest embedded processor by ARM specifically developed to address digital signal control markets that demand an efficient, easy-to-use blend of control and signal processing capabilities. The combination of high-efficiency signal processing functionality with the low-power, low cost and ease-of-use benefits of the Cortex-M family of processors is designed to satisfy the emerging category of flexible solutions specifically targeting the motor control, automotive, power management, embedded audio and industrial automation markets. The Cortex-M4 processor features extended single-cycle multiply-accumulate (MAC) instructions, optimized SIMD arithmetic, saturating arithmetic instructions and an optional single precision Floating Point Unit (FPU). These features build upon the innovative technology that characterizes the ARM Cortex-M series processors…

LED luminaires require precise power and heat management because LEDs convert most of the electrical energy they receive into heat rather than light. Without adequate thermal management, this heat can degrade the LED's life span and affect color output. Also, LEDs can fail short because they are silicon devices, so they may require fail-safe backup in the form of overcurrent protection. Resettable PPTC (polymeric-positive-temperature-coefficient) circuit-protection devices have demonstrated their effectiveness in a variety of LED-lighting applications. Like traditional fuses, they limit current after they exceed specified limits. However, unlike fuses, PPTC devices can reset after the fault clears and the power cycles.

NXP BV (Eindhoven, The Netherlands) has said it will demonstrate a microcontroller based on the ARM Cortex-M4 at the Embedded Systems Conference in San Jose, California. NXP was one of the first companies to license the Cortex-M4 processor core and a chip has been implemented using a low-leakage 90-nm process technology. This enables performance in excess of 150-MHz clock frequency, NXP said. NXP has added proprietary power-down techniques to reduce power consumption. The ESC Silicon Valley demo will show that a 7-channel audio graphic equalizer application processing 32-bit precision audio data requires only 12 MHz of CPU bandwidth using the Cortex-M4 DSP extensions, and 60 MIPs without. The core includes DSP extensions not usually found inside a microcontroller and NXP's implementation are aimed at a broad set of applications including motor control, digital power control and embedded audio.