The Hexiwear device is a great and versatile device with two microcontrollers on it. Developing firmware on a Hexiwear means changing what was originally on it. And sometimes it happens that I’m not sure if the changes are for good. Or that I accidentally destroyed the firmware on the NXP Kinetis KW40 BLE microcontroller :-(. So I had to find a way to restore the original firmware, and this is what this post is about.
Restoring the Hexiwear Firmware with a Segger J-Link
Command line tools to build applications are great. But productivity goes up if I can use the standard Eclipse environment with GNU tools. This tutorial is about how to use standard and free GNU and Eclipse tools to build my FreeRTOS application for the ARM Cortex-M4 on i.MX7 🙂 :
Eclipse used to build FreeRTOS applications for M4 on i.MX7
From time to time I face some problems which are really hard to find. Mostly these kind of bugs are very timing sensitive and depend on interrupt execution order. Maybe a dangling pointer is overwriting memory, code is running wild, or some functions are not reentrant as they should be. For these kind of bugs, good tools are worth their weight in gold. The Percepio FreeRTOS+Trace and the Segger SystemView have helped me many times to narrow down such kind problems in my applications. Another ultimate tools is hardware trace: Now I have a Segger J-Trace Pro for ARM Cortex-M in my arsenal of bug extinguishing weapons on my desk:
Dear bugs, look what I have on my desk. Your hiding time is over! 🙂
tracing-cortex-m4-with-j-trace
Smartwatches are around for a while now. To me it is still questionable how useful the ‘big’ ones for iOS and Android are. But there are definitely the crowd funded smartwatch projects which caught my attention. Maybe it is about the ‘do-anything’ with connectivity? One of these gadgets is Hexiwear: a hackable open source device
Hexiwear Device
While it *could* be a kind of smartwatch, the value of this thing is more that it includes a plethora of sensors with two microcontroller, and I can use Eclipse with GNU tools to build my firmware :-).
Alert: Hackster.io is giving away 100 Hexiwears, but you need to hurry up (submission until July 15th 2016)!
My embedded applications are implemented mostly in C, a few in C/C++. But all of them have one or few assembly files included too: Assembly programming is the needed to do low-level things so it is a natural part of a true embedded application. For example I use often an assembly file for the application startup code.
I have run into a nasty Eclipse CDT issue which deals with assembly files projects. Here is a quizz for you: can you spot the problem in my project below?
Startup Assembly Code
With Processor Expert projects it is very easy to change the heap and stack size: There is a setting for this in the Cpu component settings, under the ‘Build options’ tab:
Heap and Stack Size with Processor Expert
As there is no Processor Expert in the NXP Kinetis SDK V2.0 (see “First NXP Kinetis SDK Release: SDK V2.0 with Online On-Demand Package Builder“), how to do the same in a SDK V2.0 project?
For my classes I had so far asked the students to install the Kinetis Design Studio (KDS) v3.0.0 and then apply several updates and upgrades available. NXP has now released the v3.2.0 of their KDS (Kinetis Design Studio):
Kinetis Design Studio v3.2.0
The v3.2.0 is including all the 3.x.x updates in a single installation which makes things easier to start with. And it now works for Mac OS X “El Capitan” and the latest GNU ARM Eclipse plugins :-).
In case you are running into this problem that launching GDB hangs with this message in Eclipse:
Launching Configuring GDB Aborting configuring GDB
If using a bootloader with an application, one thing is to to merge the bootloader with the application into a single file. I do this with the ‘SRecord’ tool like this:
srec_cat bootloader.s19 application.s19 -o merged.s19
Combining S19 Files
When I create a project in Eclipse (e.g. in Kinetis Design Studio with the GNU ARM Eclipse plugins), I have to specify the name of the project during creation time:
Project Name in Eclipse
But what if I change my mind later on and want to use a different name? How to rename the project?
MCU on Eclipse 