In an earlier tutorial I introduced using I2C with the NXP LPC55S69 on OKdo E1 board to read a Bosch BME280 environmental sensor on a Mikroe Weather Click board. The MCUXpresso Clocks, Pins and Peripheral Config tools were used to get it running. It’s all for my Weather Station project that I’ve been working on during these months of lockdown. It is starting to take shape – as you can see from the photograph:
Now I really need to start reading and writing to the BME280 sensor, and that means using the I2C driver in the lpcxpresso55s69 SDK. And so this week I’ll provide a forensic examination of the most commonly-used I2C function call.
I want to share with you a little embedded trick that I use to improve the reliability of my code. And in addition to improving reliability, the technique can be used to schedule any event to occur ‘sometime in the future’. It uses the MicroTick (UTICK) timer found on the NXP LPC55S69 microcontroller, and could be applied to any device with a simple timer.
The MicroTick timer is an elegant, thing of beauty. But there is not a driver example built into the lpcxpresso55s69 SDK, and I believe that the timer is not widely used. That means we need a tutorial!
I selected the Bosch BME280 environmental sensor as the heart of my OKdo E1-based weather station. It is convenient to use, and I can prototype with the Mikroe Weather Click board MIKROE-1978. But the sensor is accessed over I2C, and that is my least favourite of the communication interfaces. In this short tutorial, I show you how the MCUXpresso Config tools (Pins, Clocks, Peripherals) are used to set up the I2C driver from the MCUXpresso lpcxpresso55S69 SDK. And very quickly, I am able to communicate with the BME280 sensor.
FreeRTOS is pretty much everywhere because it is so simple and universal, and it runs from the smallest to the biggest systems. But it still might be that for the microcontroller device you have selected there is no example or SDK support for it from your vendor of choice. In that case: no problem: I show how you could easily add FreeRTOS plus many more goodies to it.
I’m using the NXP Kinetis K22FN512 in many projects, either with the FRDM-K22F or on the tinyK22: with 120 MHz, 512 KByte FLASH and 128 KByte it has plenty of horsepower for many projects. The other positive thing is that it is supported by the NXP MCUXpresso IDE and SDK. I have now created an example which can be used as base for your own project, featuring FreeRTOS, FatFS, MinIni and a command line shell.
This week I’m sharing my experience “getting started” with the OKdo E1 board. This board, featuring the NXP LPC55S69 150 MHz, dual Cortex M33 core microcontroller was a joy to use. OKdo have provided an online Getting Started guide, and I’ve field-tested this for you. My video tutorial recorded as I follow the guide is less than 7 minutes long… it may take you a little longer if you need to download MCUXpresso IDE or the lpcxpresso55s69 Software Development Kit (SDK) but I am confident that you will quickly have the board up-and-running.
Especially in a lab or classroom environment it is convenient to start with a template project, and then explore different ways to shape the project for different needs. As for any IDE of this world, this requires an understanding of the inner workings to get it right. So in this article I show how to copy, clone or rename properly an Eclipse ‘template’ project in the MCUXpresso IDE.
The tinyK22 board with the NXP K22FN512 is a bread-board-friendly small board with a 8 MHz external oscillator:
This tutorial is about how to use the NXP MCUXpresso Clock configuration and configure the board to the maximum clock frequency of 120 MHz. The same steps apply to many other boards, including the FRDM-K22F one.
In last week’s blog I explained that the LPC55S69 microcontroller from NXP has two Cortex® M33 cores, named core0 and core1. There was a lot of theory, and so this week I put it all into practice and show you how to debug 2 cores with MCUXpresso IDE.
Throughout this series I’ve been using the LPC55S69 microcontroller from NXP as a platform to investigate the ARM Cortex® M33 core. NXP designed the LPC55S69 with two Cortex M33 cores and so this week I’m investigating these in more detail.
You’ll remember that when ARM launch a processor core it will have a number of optional features. This is shown very clearly on the LPC55S69. The 150 MHz primary core – cpu0 – is a full implementation of Cortex® M33 and includes the optional components FPU, MPU, DSP, ITM and the TrustZone® features.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.