The evolving landscape of DSP

DSP is all about multiplying, accumulating, and manipulating data for all kinds of interesting applications such as software defined radios, controlling motors and encoding and decoding music. It has become something that touches all of our lives. We can’t even watch TV without it. Everything is digital. These days when you talk about inductors designers give you a funny look. Power supply designers are the only ones that can describe what saturating a core means. DSP is in most designers’ thoughts because of the world we live in.

As an example, a designer is using an 8051 for a home alarm system and then marketing comes along and says they want it to play an MP3 file for the alarm sound. “I guess that means I need to get a DSP to do that job and have my 8051 tell it to play the sound, but wait a minute marketing says it still needs to cost the same.” Having a standalone DSP would double the cost of the processor BOM. The question then becomes why can’t the DSP do the same functions as my 8051, or a better statement is, “Can’t I get a microcontroller that can do DSP functions?” Because of these questions semiconductor vendors are moving DSP’s into the microcontroller space and microcontrollers are moving into the DSP. Both points have merits. The designers that are familiar with DSP architectures will certainly like the fact that the DSP has more microcontroller like functions such as embedded flash and connectivity, but designers more comfortable with microcontrollers get the added advantage that they can get upgrades on existing architectures they are familiar with but get more horse power for the required DSP functions that the market demands.

To illustrate the point, ARM7 started to appear as a fully fledged microcontroller in early 2000 in parts such as NXP’s LPC2106 that had up to 128 kbytes of flash and all the traditional serial communication devices found on microcontrollers. Previously ARM7 was used for MP3 decoding and encoding in dedicated ASIC’s. This was the start of low cost microcontrollers that had capabilities to perform some DSP tasks. Over the last 7 years ARM has moved to the Cortex family such as the Cortex M3 which offers improvements over ARM7 for certain DSP applications. In addition, M3 based microcontrollers can operate up to 120 MHz which further enhances its DSP capabilities.

With the instruction set and performance of the M3, designers now have the opportunity to enhance a microcontroller based product with applications that require DSP functions. These could range from simple digital filters to PID controllers and MP3 decoding. However, all this stuff requires software and the traditional designer of microcontroller based products are looking for off the shelf solutions that don’t require extensive DSP knowledge. Microcontroller vendors and third party DSP experts are stepping in to help. The semiconductor vendors are providing free DSP libraries and application examples and third party vendors that were just supporting traditional DSP’s are adding microcontrollers to their list of supported devices. More of this will follow as designers discover the capabilities of these new devices.

The market for digital devices is expanding and changing. Will anyone be happy with standard definition TV once they get use to HD TV? There will always be a need for standalone DSP’s that further push the limits of speed and performance, and they will exist in ASIC’s or multi-core standard offerings. Even designers of power supplies are seeing DSP’s enter their domain, where the loop is being closed around digital controllers. Power supply designers may use DSP’s in their products but, they will always have to know about designing inductors (Yea). One thing is for sure, microcontrollers will add more DSP functionality and DSP’s will add more microcontroller functionality. This will give designers many options to add interesting and compelling features to their products’ and a key factor in choosing will be the software and infrastructure available for that architecture.

Rob Cosaro, Systems Applications & Architecture Manager, NXP