Be aware: Floating Point Operations on ARM Cortex-M4F

My mantra is *not* to use any floating point data types in embedded applications, or at least to avoid them whenever possible: for most applications they are not necessary and can be replaced by fixed point operations. Not only floating point operations have numerical problems, they can lead to performance problems as in the following (simplified) example:

#define NOF  64
static uint32_t samples[NOF];
static float Fsamples[NOF];
float fZeroCurrent = 8.0;

static void ProcessSamples(void) {
  int i;

  for (i=0; i<NOF; i++) {
    Fsamples[i] = samples[i]*3.3/4096.0 - fZeroCurrent;
  }
}

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Remote Debugging with USB based JTAG/SWD Debug Probes

For some projects it is not possible to have the device under debug available on my desk: the board might be in another room, on another site or in a place where physical access is not possible or even dangerous. In that case an IP-based debug probe (see Debugging ARM Cores with IP based Debug Probes and Eclipse) is very useful: as long as I can access its IP address, that works fine. It is an excellent solution even if the board is moving or rotating: hook it up to a WLAN access point and I still can use it as it would be on my desk.

But what if I have a debug probe only connected to USB? This article shows how to turn a USB debug probe into a IP-based debug solution: that way I can easily debug a board from remote, connected to the network:

IP Based Debugging with USB Debug Probe

IP Based Debugging with USB Debug Probe

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Debugging the Startup Code with Eclipse and GDB

By default, when debugging an embedded application, the target usually stops at main():

stopped in main

stopped in main

That’s usually fine, but what if I want to debug the code out of reset?

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Tutorial: HD44780 Display Driver with NXP MCUXpresso SDK

In the age of high-resolution graphical LCDs using a character display might look like a bit anachronistic. But these displays provide a lot of value for me as they are robust, available in different shapes and number of lines. And such a character display can be a better solution for an industrial application.

hd44780 display with NXP FRDM-KW41Z Board

hd44780 display with NXP FRDM-KW41Z Board

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FreeRTOS: how to End and Restart the Scheduler

Most host or desktop systems (say Linux, Mac or Windows) have a normal use case where you start the operating system say in the morning and shut it down in the evening, and then you leave the machine. Embedded Systems are different: they are not attended, and they are supposed to run ‘forever’. Not every embedded system needs to run an OS (or in that world: Real-Time Operating System or RTOS), but the same applies here: after the RTOS is started, it is not intended that it will shutdown and restart. To the extend that you won’t they support the ‘shutdown’ and ‘restart’ functionality at all. In case of gathering coverage information this would be really useful:

coverage information from freertos application

coverage information from FreeRTOS application

In the case of FreeRTOS: what if I really need to shutdown the RTOS and restart it again, as by default this is not supported. This is what this article is about …

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McuOnEclipse Components: 30-Sept-2018 Release

I’m pleased to announce a new release of the McuOnEclipse components, available on SourceForge. This release includes several bug fixes, extra support for the NXP S32 Design Studio and SDK and includes FreeRTOS V10.1.1.

SourceForge

SourceForge

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Updating the S32K144EVB to Switch between 5V and 3.3V Logic Levels

By default, the NXP S32K144EVB and microcontroller is using a 5V supply voltage and logic levels which is great for noisy environment or any 5V devices. Many of my displays and sensors use 3.3V logic levels, so I would have to use a level shifter from 5V to 3.3V. There is another way: to change the board for 3.3V logic levels so I can use directly things like a SSD1306 display.

S32K144EVB with OLED SSD1306 using 3.3V Logic Levels

S32K144EVB with OLED SSD1306 using 3.3V Logic Levels

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Using custom FreeRTOS with S32K SDK and OSIF for ARM

In “Tutorial: FreeRTOS 10.0.1 with NXP S32 Design Studio 2018.R1” I showed how to use a custom FreeRTOS with the S32 Design Studio (ARM). The OSIF (OS Interface) provides an operating system and services abstraction for the application which is used by other S32K SDK components:

OSIF in S32K for ARM Eclipse Project

OSIF in S32K for ARM Eclipse Project

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Tutorial: FreeRTOS 10.0.1 with NXP S32 Design Studio 2018.R1

NXP not only sells general purpose microcontroller, but as well a portfolio of automotive devices which includes the S32K which is ARM Cortex based. For this device family, they offer the S32 Design Studio (or S32DS) with its own Eclipse distribution and SDK. The interesting part is that the S32DS includes Processor Expert (which is a bit different from the ‘mainstream’ Processor Expert). It comes with its own components for the S32K SDK which includes a component for FreeRTOS. But that component in S32DS 2018.R1 comes with an old V8.2.1 FreeRTOS component:

FreeRTOS 8.2.1 in S32DS 2018.R1

FreeRTOS 8.2.1 in S32DS 2018.R1

So what to do if I want to use the latest FreeRTOS (currently 10.0.1) with all the bells and whistles?

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McuOnEclipse Components: 1-July-2018 Release

I’m pleased to announce that a new release of the McuOnEclipse components is available on SourceForge. This release includes several smaller bug fixes and initial component support for the NXP S32 Design Studio and SDK.

SourceForge

SourceForge

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Show FreeRTOS Threads in Eclipse Debug View with SEGGER J-Link and NXP S32 Design Studio

By default, the FreeRTOS threads do not show up with the SEGGER J-Link debug connection in the Eclipse based NXP S32 Design Studio IDE. But don’t worry: Here is how to get it working with SEGGER J-Link debug connection:

FreeRTOS Threads in Eclipse Debug View

FreeRTOS Threads in Eclipse Debug View

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Performance and Runtime Analysis with FreeRTOS

One of the great things with the FreeRTOS operating system is that it comes with free performance analysis: It shows me how much time is spent in each task. Best of all: it shows it in a graphical way inside Eclipse too:

FreeRTOS Runtime Information in Eclipse

FreeRTOS Runtime Information in Eclipse

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McuOnEclipse Components: 25-Sept-2017 Release

I’m pleased to announce that a new release of the McuOnEclipse components is available in SourceForge. In this release more ARM Cortex devices/vendors are supported with different SDKs, plus it comes with several FreeRTOS enhancements for debugging highly optimized code.

SourceForge

SourceForge

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Adding CMSIS-SVD Files to EmbSysRegView 0.2.6.r192 and Eclipse

In “EmbSysRegView 0.2.6 for Eclipse Neon and Oxygen” I have described how to add CMSIS-SVD register detail files to Eclipse using the EmbSysRegView plugin.

But what I need to add vendor or any other SVD files to it? Here is how:

EmbSys Registers View

EmbSys Registers View

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