Category Archives: Tips & Tricks

Eclipse JTAG Debugging the ESP32 with a SEGGER J-Link

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When Espressif released in 2014 their first WiFi ESP8266 transceiver, they took over at least the hobby market with their inexpensive wireless devices. Yet again, the successor ESP32 device is used in many projects. Rightfully there are many other industrial Wi-Fi solutions, but Espressif opened up the door for Wi-Fi in many low cost projects. Many projects use the ESP devices in an Arduino environment which basically means decent debugging except using printf() style which is … hmmm … better than nothing.

What is maybe not known to many ESP32 users: there *is* actually a way to use JTAG with the ESP32 devices :-). It requires some extra tools and setup, but with I have a decent Eclipse based way to debug the code. And this is what this article is about: how to use a SEGGER J-Link with Eclipse and OpenOCD for JTAG debugging the ESP32.

Roboter with ESP32 and JTAG Debug Port

Robot with ESP32 and JTAG Debug Port

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Building and Flashing ESP32 Applications with Eclipse

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The new semester is approaching in a very fast way, and so is the new lecture and lab module ‘Advanced Distributed Systems’ at the Lucerne University. For that module we are going to build a new ‘Sumo’ style robot with WLAN capabilities using the ESP32 chip. It will be a new robot PCB, and below is the current robot (based on NXP K22FX512) with the WLAN module connected to it:

Zumo connected to TTGO ESP32 module

Zumo connected to TTGO ESP32 module

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Tutorial: How to Optimize Code and RAM Size

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It is great if vendors provide a starting point for my own projects. A working ‘blinky’ is always a great starter. Convenience always has a price, and with a ‘blinky’ it is that the code size for just ‘toggling a GPIO pin’ is exaggerated. For a device with a tiny amount of RAM and FLASH this can be concerning: will my application ever fit to that device if a ‘blinky’ takes that much? Don’t worry: a blinky (or any other project) can be easily trimmed down.

Binky on NXP LPC845-BRK Board

Binky on NXP LPC845-BRK Board

I use a ‘blinky’ project here just as an example: the trimming tips can apply to any other kind of projects too.

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Restoring Default Firmware on Seeed Arch Mix NXP i.MX RT1052 Board

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In my previous article “Debug and Execute Code from FLASH on the Seeed Arch Mix NXP i.MX RT1052 Board” I explained how to take complete control over the board and flash and debug a firmware. Of course this overwrites the one which comes by default shipped on the board. This article is about how to restore or update the original firmware.

Restored Seeed Firmware

Restored Seeed Firmware

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Visualizing Global Variables while Target is Running with Eclipse and MCUXpresso IDE

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By default, Eclipse provides ‘stop-mode-debugging’: in order to inspect the target code and data, I have to stop the target. But with the right extensions as present in the Eclipse based MCUXpresso IDE, it is possible to inspect the target even while it is running.

Graphing Variables

Graphing Variables

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Generating Intel Hex Files with a given Length using srec_cat

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The ‘standard’ binary files for many tools are S19, binary or Intel Hex files. Especially for S19 and Intel Hex it can be useful to control the amount of data per line. By default, the GNU objcopy creates files with a line length of 44 characters:

default objcopy binary file line length

default objcopy binary file line length

But it is possible to have Intel Hex files with an custom line length using the SRecord utility, and this is what this article is about.

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Black Magic Open Source Debug Probe for ARM with Eclipse and GDB

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The ‘Black Magic Probe’ (or in short: BMP) is a very small and open source JTAG/SWD debug probe with a build-in GDB Server. I saw that probe referenced in different places, so I thought I try it out with a few of my NXP LPC and Kinetis boards:

BMP with LPC and Kinetis Boards

BMP with LPC and Kinetis Boards

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SWO with NXP i.MX RT1064-EVK Board

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With the cost of an single pin, many ARM Cortex-M boards including the NXP i.MX RT1064 can produde SWO data: think about a pin able to stream data out of the chip in realtime. For example interrupt activity which otherwise might be hard to capture:

SWO Interrupt Trace

SWO Interrupt Trace

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Reverse Engineering of a Not-so-Secure IoT Device

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The ‘Internet of Things’ is coming! It started as an overused marketing hype with no real use case (who needs internet connected fridges? Who wants the internet connected toilet paper?).

New ‘things’ start to pop up, useful or not: From smart bulbs (Philips Hue), thermostats (Nest), smart TV (Samsung and others) up to voice assistants (Alexa, Cortana, Google). You might even have installed one of these, right? What about temperature and humidity sensors? Probably there is nothing wrong with that?

But what would you think if one morning you find a strange unknown device installed under your working desk, connected to the cloud and internet?

IoT Device attached under a working desk

IoT Device attached under a working desk

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MCUXpresso Eclipse IDE Mouse Tips & Tricks

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In a modern development workflow both command-line and a graphical user interface has its place. On the GUI side, Eclipse is famous that it offers many different ways to accomplish something which is great. But sometimes I continue to use an old habit or way because I have missed that there is a newer and better way, and the MCUXpresso Eclipse IDE is no exception to that. In this article I show a few ways how to use the mouse even more productive.

Project Settings

Project Settings

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Internal and External Debug Options for the NXP LPC55S69-EVK Board

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The LPC55S69-EVK board comes on-board debug probe. The board includes the LPC4322JET100 device which acts like NXP LPC-Link2 debug probe:

LPC4322JET100 on LPC55S69-EVK

LPC4322JET100 on LPC55S69-EVK

But it is easily possible to use the board with an external debug probe or re-program the onboard one as a SEGGER J-Link debug probe.

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Building a Raspberry Pi UPS and Serial Login Console with tinyK22 (NXP K22FN512)

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There are different ways to ruin a Linux system. For the Raspberry Pi which uses a micro SD card as the storage device by default, it comes with two challenges:

  1. Excessive writes to the SD card can wear it out
  2. Sudden power failure during a SD card write can corrupt the file system

For problem one I do I have a mitigation strategy (see “Log2Ram: Extending SD Card Lifetime for Raspberry Pi LoRaWAN Gateway“). Problem two can occur by user error (“you shall not turn it off without a sudo poweroff!”) or with the event of a power outage or black out. So for that problem I wanted to build a UPS for the Raspberry Pi.

Raspberry Pi with UPS System and tinyK22

Raspberry Pi with UPS System and tinyK22

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Tutorial: MCUXpresso SDK with Linux, Part 1: Installation and Build with Make

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I admit: my work laptop machine is running a Windows 10 OS by default. But this does not prevent me running Linux in a Virtual Machine (VM). Each host platform has its benefits, and I don’t feel biased to one or the other, but I have started using Ubuntu more and more, simply because I have worked more on Embedded Linux projects. While I have used mostly Windows with Eclipse for NXP LPC, Kinetis and i.MX platforms in the past, I started using Ubuntu too from last year with the NXP MCUXpresso SDK. I did not find much documentation about this on the web, so I thought it might be a good idea to write a tutorial about it. So here we go…

Building NXP MCUXpresso SDK on Linux Ubuntu

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Log2Ram: Extending SD Card Lifetime for Raspberry Pi LoRaWAN Gateway

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My LoRaWAN gateway (“Contributing an IoT LoRaWAN Raspberry Pi RAK831 Gateway to The Things Network” is running and working great now for more than a month and it already has transmitted more than 30k messages:

Gateway Overview

Gateway Overview

This creates a lot of log entries on the micro SD card of the Raspberry Pi. To avoid writing too many times log data, I have installed Log2Ram.

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Be aware: Floating Point Operations on ARM Cortex-M4F

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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

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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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Contributing an IoT LoRaWAN Raspberry Pi RAK831 Gateway to The Things Network

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LoRa and LoRaWAN is getting the de-facto wireless IoT network in my area. No surprise that traditional telecom providers like Swisscom trying to monetize the ‘Internet of Things’ area. Luckily there is an open and free alternative: https://www.thethingsnetwork.org/. Volunteers, enthusiasts and members in the different TTN communities build gateways and offer free LoRaWAN network access. I wanted to contribute to that grassroots movement with building my gateway, providing LoRaWAN access to my neighborhood.

LoRaWAN TheThingsNetwork Gateway

LoRaWAN TheThingsNetwork Gateway

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Different Ways of Software Configuration

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Most of the time software needs some way to configure things: depending on the settings, the software will do different things. For example the software running on the microcontroller on top of the Raspberry might have the OLED LCD available or not:

Raspberry Pi and tinK22 with OLED LCD

Raspberry Pi and tinyK22 (NXP Kinetis K22FN512) with OLED LCD

How can I deal with this in my application code? Continue reading →

Debugging the Startup Code with Eclipse and GDB

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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: Changing ARM Cortex Core or Microcontroller in Eclipse CDT Projects

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Sometimes I start a project with an ARM microcontroller, and in the middle of the project I find out that it was a wrong choice at the beginning and I need to switch the microcontroller derivative or even the used ARM core. With little knowledge of the project structure and the files needed, such a switch is not the easiest thing, but definitely possible.

switching cores

switching cores

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