Investigating ARM Cortex® M33 core – DSP Acceleration 3 (PowerQuad FFT Tutorial)

I’ve always felt that the Fourier Transform (and in particular the embedded implementation Fast Fourier Transform) is the GOAT* of the DSP algorithms. The ability to convert a time-domain signal into a frequency-domain signal is invaluable in applications as diverse as audio processing, medical electrocardiographs (ECGs) and speech recognition.

So this week I’ll show you how to use the Transform engine in the PowerQuad on LPC55S69 to calculate a 512-point FFT. All of the difficult steps are very easily managed and the PowerQuad does all of the very heavy lifting.

Data from PowerQuad – 512-point real FFT on 400 Hz input signal with 1200 Hz harmonic
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Investigating ARM Cortex® M33 core – DSP Acceleration 2 (PowerQuad Matrix Engine Tutorial)

Last week I showed you how to use the Coprocessor interface of PowerQuad to calculate (mostly) unary functions. As an example the natural logarithm ln(x) takes just one operand, whilst the floating divide in PowerQuad requires two operands (x1)/(x2). PowerQuad is very efficient accelerating these functions, requiring just 6 clock cycles for the ln(x) and 6 clock cycles for the float (x1)/(x2). In comparison the single-precision floating point unit in Cortex® M4F and M33F requires 13 clock cycles to perform the same float divide.

But there are two ‘sides’ to the PowerQuad:

  • The Coprocessor interface, using ARMv8-M coprocessor instructions;
  • The AHB bus interface, where we address PowerQuad as a peripheral.

So this week… operating the PowerQuad as a peripheral. I’ll show you how to use the PowerQuad SDK driver in MCUXpresso in a new project, and use the Matrix Engine in the PowerQuad to solve simultaneous equations.

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OpenPnP Solder Paste Dispensing Video

OpenPnP (see “Building a DIY SMT Pick&Place Machine with OpenPnP and Smoothieboard (NXP LPC1769)“) is a cool open source framework to run Pick&Place machines. I have mentored and supported Tobias Mailänder who extended the PnP machine with the ability to dispense solder past on PCBs. Below a video (courtesy of Tobias Mailänder) which shows the machine in action:

It is still a prototype, but things are working very well.

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World Stepper Clock with NXP LPC845

I really love clocks. I think this is I am living here in Switzerland. Beside of that: clock projects are just fun :-). After I have completed a single clock using stepper motors (see “DIY Stepper Motor Clock with NXP LPC845-BRK“), I wanted to build a special one which is able to show up to four different time zones: Below an example with London (UK), New York (USA), Beijing (China) and Lucerne (Switzerland):

Stepper Clock

Stepper Clock

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Investigating ARM Cortex® M33 core with TrustZone® – DSP Acceleration 1

If you ask your colleagues about ARM Cortex® M33 core, they’ll most likely remember that the ARMv8-M architecture adds the (optional!) TrustZone® security extension. But one, overlooked but significant new feature in ARMv8-M is the new coprocessor interface.

ARMv8-M adds many new features to the core architecture, including Co-processor interface

With the LPC55S69 microcontroller, NXP decided to add an extremely powerful DSP Accelerator onto this coprocessor interface, named PowerQuad. In this week’s video series I’m investigating the PowerQuad, and the functions that it provides.

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Open Source LittlevGL GUI Library on Adafruit Touch LCDs with NXP LPC55S69-EVK

The NXP LPC55S69-EVK is a versatile board. In this article I show how it can be used with Adafruit TFT LCD boards, both with resistive and capacitive touch. For the software I’m using the open source LittlevGL GUI.

LPC55S69-EVK with Adafruit Touch LCD

LPC55S69-EVK with Adafruit Touch LCD

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Investigating ARM Cortex® M33 core with TrustZone® – In-Application Programming Tutorial

Last week I investigated the In-System Programming feature in the boot ROM of the LPC55S69. Using the command-line program blhost I was able to erase the flash and download simple LED blinky programs. Of course, the functions that erase and program the flash are present in the boot ROM.

Wouldn’t it be great if we could call those program and erase functions from our own software running on the LPC55S69?

Of course, we can. This is the NXP feature In-Application Programming, and this week I’ll show you how to interface to the Flash Driver in the boot ROM from software. Since the program and erase functions are running from ROM, this avoids the normal considerations about using flash for non-volatile storage.

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Open Source FTDI FT2232 JTAG and UART Adapter Board

In JTAG Debugging the ESP32 with FT2232 and OpenOCD I have used a FTDI FT2232 breakout board to JTAG debug with OpenOCD. With an adapter board on top of the TDI FT2232 the wiring is much easier and simpler to use:

JTAG Debugging the ESP32 with FT2232

JTAG Debugging the ESP32 with FT2232

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Investigating ARM Cortex® M33 core with TrustZone® – In-System Programming Tutorial

This week I’m back to the normal ‘Tutorial’ format with a look at the In-System Programming feature in the boot ROM of the LPC55S69. I’ll use the NXP-provided command-line program blhost and interface with the ROM to erase the flash and download simple LED blinky programs.

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TrustZone® vs HeartBleed

During my research about the TrustZone® security extension over the last weeks I’ve had the HeartBleed exploit from 2014 in my mind. How would TrustZone® help us manage that type of ‘no bounds check’ exploit? Of course, TrustZone® was first widely available when NXP introduced the Cortex® M33 family LPC55S69 in 1Q2019 and wasn’t available back in 2014, but I wanted to put it to the test.

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Using SEGGER J-Link with QSPI FLASH on NXP i.MX Boards

In “Seeed Studio Arch Mix NXP i.MX RT1052 Board” and “Debug and Execute Code from FLASH on the Seeed Arch Mix NXP i.MX RT1052 Board” I have used the NXP LPC-Link2 to debug the Seeed Arch Mix board with the NXP i.MX RT1052, because the SEGGER J-Link does not work out-of-the box with the i.MX RT using QSPI Flash. This article shows how the J-Link connection can be changed from HyperFlash to work with QSPI Flash.

J-Link EDU Mini with Seeed i.MX RT1052

J-Link EDU Mini with Seeed i.MX RT1052

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Investigating ARM Cortex® M33 core with TrustZone® – Trusted Execution Environment tutorial

When we are learning about TrustZone® it does not take long to recognise that it is the security attributes for memory that define memory regions to be Secure, Non-Secure or Non-Secure Callable. This week’s video shows how the Cortex® M33 core with TrustZone® extension can test the security attributes for every read, write and execute from memory (without impacting performance). And how the security attributes are set with the Trusted Execution Environment configuration tool inside MCUXpresso IDE.

Trusted Execution Environment configuration tool in MCUXpresso IDE
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JTAG Debugging the ESP32 with FT2232 and OpenOCD

In “Eclipse JTAG Debugging the ESP32 with a SEGGER J-Link”  I used a SEGGER J-Link to debug an ESP32 device with JTAG. I looked at using one of the FTDI FT2232HL development boards which are supported by OpenOCD. The FT2232HL is dual high-speed USB to UART/FIFO device, and similar FTDI devices are used on many boards as UART to USB converters. With OpenOCD these devices can be turned into inexpensive JTAG debug probes. This article shows how to use a $10 FTDI board as JTAG interface to program and debug the Espressif ESP32.

FTDI JTAG Connection

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Investigating ARM Cortex® M33 core with TrustZone® – transition from non-secure to secure world

You might purchase a Cortex® M33 microcontroller with TrustZone® where the supplier has installed a secure ROM. Or you might be an IOT developer using LPC55S69 in your own application where you have partitioned the code into secure and non-secure partitions. At some point with Cortex® M33 core with the TrustZone® security extension you’ll want to transition from non-secure into the secure world. Or (put more elegantly), you’ll want to call one of the secure functions supported when the Cortex® M33 core is in the Secure state.

That’s the topic for this week’s video.

How will you know what secure functions are available? And what parameters are necessary to call these functions? You’ll be provided with a header file veneer_table.h and a secure object library named project_name_CMSE_lib.o. Together these 2 modules describe everything that you need to know to call a secure function and transition from the Non-Secure to the Secure state.

Just two objects – *.o and *.h define resources available in the Secure world
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Investigating ARM Cortex® M33 core with TrustZone® – running TrustZone® example projects in MCUXpresso IDE

Last week I wrote about why we need the TrustZone® security extension for ARMv8-M. There are software use-cases where it can be very helpful to partition the software into 2 separate worlds, secure and non-secure. TrustZone® acts as the gatekeeper between these two worlds and manages how the core transitions between the worlds. The ARMv8-M architecture introduces two new States for the core – secure and non-secure. Cortex® M33 core (and M23 core also) is implemented to ARMv8-M standard and of course supports the two new states.

ARMv8-M architecture introduces 2 states for the core – secure and Non-secure
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Linking Bootloader Applications with Eclipse and FreeMarker Scripts

Bootloaders are a fine thing: With this I can load any applications I like. Power comes with some complexity, and a bootloader alone is a complex thing already. But this applies to the application part too: I need to link the application to a certain offset in the memory space so it can be loaded by the bootloader, plus the application typically needs to add some extra information to be used by the bootloader. This article describes how to build a bootloader application with Eclipse (MCUXpresso IDE) using the MCUXpresso SDK.

Build Configuration for Bootloader Application

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Investigating ARM Cortex® M33 Core with TrustZone® – What is TrustZone® anyway?

After the Getting Started material from the previous weeks, today we are ready to investigate TrustZone®. We all remember TrustZone® – it is that magic piece of embedded IP that miraculously solves all of our IOT security problems – right? It’s true that TrustZone® is an embedded component related to security, but not in the way that you think.

Non-trusted software can dump out our keys to a cloud server hosted by malign third-party

Before we get stuck into all the fancy technical details, let us at first stop and think about some of the challenges that we face with embedded systems, and what can be done about them. This week I simply address the topic: What is TrustZone® and Why do we need it??

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Stack Canaries with GCC: Checking for Stack Overflow at Runtime

Stack overflows are probably the number 1 enemy of embedded applications: a call to a a printf() monster likely will use too much stack space, resulting in overwritten memory and crashing applications. But stack memory is limited and expensive on these devices, so you don’t want to spend too much space for it. But for sure not to little too. Or bad things will happen.

The Eclipse based MCUXpresso IDE has a ‘Heap and Stack Usage’ view which can be used to monitor the stack usage and shows that a stack overflow happened:

Heap and Stack Usage

Heap and Stack Usage

But this is using the help of the debugger: how to catch stack overflows at runtime without the need of a debugger? There is an option in the GNU gcc compiler to help with this kind of situation, even if it was not originally intended for something different. Continue reading

Investigating ARM Cortex® M33 core with TrustZone® – Using the Clocks Config Tool

Clocks. I’ve always found the clock setting of a microcontroller one of the hardest things to get right during my embedded career. If I re-use the clocks setup from the development board it is easy. But if the development board runs from a crystal and I want to use the free-running internal clock, or if I change to a different frequency crystal (and keep the same PLL output frequency) it always gets difficult. To be honest I’ve developed some projects early in my career and never been 100% certain at what frequency the core, flash and peripherals are running.

That’s not good.

The Config Tools within the MCUXpresso brand have greatly simplified setting up the pins, clocks, peripherals (and next week – Trusted Execution Environment 🙂 ) on NXP microcontrollers. So I’m going to quickly show you how to set up 3 different clock arrangements, and output the main clock to an output pin named CLK_OUT.

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