How the PowerQuad Co-processor Frees Up CPU Cores within the LPC55S69 MCU

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Other than its two processing cores, numerous safety elements, and different helpful options, NXP’s LPC55S69 PowerQuad comes with a built-in DSP. 

The “PowerQuad” is a chosen {hardware} co-processor that aids the CPU cores in performing a regular set of difficult mathematical operations, similar to mathematical operations, matrix calculations, filtering, and rework capabilities, together with FFT. Utilizing the PowerQuad unit to carry out such usually CPU-heavy duties leaves the primary cores free to finish different duties. 

On this article, be taught in regards to the PowerQuad unit and one of many many initiatives that may be realized by using it.


What’s the PowerQuad?

PowerQuad is a devoted {hardware} element that may effectively carry out calculations that might take a traditional CPU a major time to course of. As an alternative of letting one of many MCU’s Arm® Cortex®-M33 cores do the job, the LPC55S69’s built-in PowerQuad unit can run calculations in parallel to the primary CPU, releasing up the CPU for different duties, similar to communication and IO operations. 

With the assistance of the PowerQuad, embedded software builders can implement refined sign processing algorithms with out having to pressure the CPU, which is a vital use-case in distributed sensor programs and the Industrial Web of Issues (IIoT).


Instance Venture: Utilizing the PowerQuad in a Mini-Monkey Board 

The LPC55S69 MCU and its PowerQuad co-processor have the potential to allow all kinds of embedded initiatives and merchandise, and this text takes a take a look at one among them. 

With the assistance of a Mini-Monkey board that makes use of an LPC55S69 MCU and comprises an OLED show and a microphone, a demo software was developed. It samples the audio from the microphone and shows a waveform of the sampled audio on the OLED show. Intimately, 256 samples are collected with a sampling price of 32KHz earlier than the uncooked time collection knowledge is displayed. The decision in amplitude is 18-bits, and the amplitude needed to be divided down to suit the waveform on the output show.


Determine 1. The LPC55S69 MCU permits the mini-monkey board to pattern time-series knowledge from a microphone and show it on the built-in display screen. 


The purpose of this experiment is to work with time-series knowledge. This instance collects knowledge right into a buffer after which frequently shows the knowledge on the display screen. Right here, the information occurs to return from a microphone. It’s, nonetheless, doable to make use of another sensor as effectively. 


A Have a look at Time-Sequence Knowledge

Time-series knowledge is commonplace in lots of sensor-based and IIoT functions. It describes a type of measurement the place data is collected at a continuing interval and put right into a buffer. Relying on the context, the person knowledge samples is perhaps processed immediately, or a broader set of data is processed directly, for instance, as soon as the buffer is full.

In the long run, there’s a buffer crammed with knowledge samples that characterize the change of the enter over a sure interval. Observe that it’s unattainable to take samples infinitely quick, and the measurement decision can’t be arbitrarily excessive. Nonetheless, for the sampling to work, the sampling frequency should be quick sufficient to sufficiently seize the quickest frequency within the sampled sign (refer to the Nyquist-Shannon sampling theorem).


A simplified example of time-series data.

Determine 2. A simplified instance of time-series knowledge.


Discover that the dots within the determine above aren’t linked, indicating that the captured knowledge is discrete.


How the PowerQuad Aids in Processing Knowledge

Many sign processing algorithms boil right down to comparatively easy however repetitive calculations over arrays of knowledge. Nearly any complicated operation might be damaged down right into a collection of multiplication and add operations, which is why MAC models are a vital a part of digital sign processors and even many fashionable general-purpose CPUs.

The LPC55S69 PowerQuad co-processor incorporates the most typical constructing blocks for performing DSP calculations. It really works alongside the MCU to hurry up filtering or remodeling time-series knowledge. This permits the 2 Cortex-M33 cores to carry out different duties, similar to amassing and buffering extra knowledge samples, whereas the PowerQuad crunches the numbers in parallel. It’s clear to see how this quickens many functions that require DSP functionalities.

The rise in processing velocity, nonetheless, isn’t the one profit. By together with the PowerQuad unit within the LPC55S69 MCU, embedded engineers can goal for smaller and extra power-efficient designs as a result of they don’t have to incorporate an exterior DSP. Purposes that don’t essentially require a DSP to work may also profit from the PowerQuad by using it to filter out noisy knowledge, permitting transmission and storage of solely related data.


Energy Line Communications and Metering

One other use-case for the LPC55S69 MCU is energy line communications (PLC), which might be helpful if there’s no wiring infrastructure apart from AC or DC energy strains. PLC makes use of refined methods similar to orthogonal frequency division multiplexing (OFDM) for transmitting knowledge over energy strains. OFDM is noise-tolerant, and it permits a system to ship knowledge bits down a communications channel in parallel throughout a number of frequency bands. Because of this strategy, many sluggish parallel communications channels might be utilized to realize excessive bit charges.

OFDM options require the system to compute FFTs in real-time on an incoming time-series, which is the place the PowerQuad comes into play. It aids the CPU in encoding the information that’s to be despatched over an influence line. 

Utilizing bins of the FFT, the outgoing data is encoded utilizing the actual and imaginary elements (amplitude and part) to kind the bits of an information phrase. As soon as that is accomplished, an inverse FFT might be utilized to finish up with a time-series sign despatched by a DAC. On the decoding finish, an FFT must be carried out to get the unique bins. As soon as that’s accomplished, the unique knowledge might be reconstructed utilizing the amplitude/part data.

Though that is an excessive simplification of the OFDM course of, it exhibits that accelerators such because the PowerQuad are very important in making it work. The LPC55S69 MCU is, due to this fact, very effectively suited to functions like this. The filtering, decoding, and encoding are all outsourced to the PowerQuad unit, guaranteeing that the 2 central CPU cores are free to do different issues within the meantime. Moreover, all of this may be achieved utilizing little or no power and with out the necessity for extra exterior co-processors.


The LPC55S69 PowerQuad Unit

This text mentioned two examples enabled by the LPC55S69 MCU and its embedded PowerQuad unit, which can be utilized to speed up the mathematical operations required in digital sign processing. 

Utilizing the PowerQuad unit to carry out such computation-heavy operations leaves the LPC55S69 MCU’s two principal Cortex-M33 cores free to finish different duties. The strategy of together with a DSP within the LPC55S69 MCU has many advantages, together with decreased energy consumption, quicker computations, and easier designs.

NXP’s community page gives an in-depth take a look at the LPC55S69 MCU’s PowerQuad unit and its capabilities. The location additionally gives numerous software notes, tutorials, and movies primarily based on the accessible MCUs to assist customers higher perceive their capabilities. 

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