On the FRDM-KL25Z Board the target processor supports both USB host and device mode. However, the Freedom board has no jumper or other means to power the USB bus (which is required in the USB host mode). So if I want to get access to a memory stick from the KL25Z, then I’m stuck because the board does not offer that option. Luckily there is an easy hack to work around this.
Looking at the FRDM-KL25Z board schematics, there is 5V available on Pin 10 of J9:
5V on J9 Pin 10 on FRDM-KL25Z Board
Sometimes I show to much in a tutorial: only writing something to the UART? Sounds boring, so why not adding tasks, LEDs and a full shell implementation to the mix as in this post? Yes, definitely too much to start with at the beginning :-(. So less is more, and if it is just about the UART. And I promise: it is doable with around 50 lines of application code :shock:.
AND: I admit, this post title is a trap ;-). It is not about printf(). But it *is* about using the UART on the KL25Z Freedom board and to do things like printf(), and even more. Trust me. It is about how to write *and* read from the UART. While I’m using here the Kinetis-L ARM Cortex-M0+ KL25Z Freedom board, it is applicable to any other Kinetis device.
Yes, I’m using Processor Expert *a lot*. But there might be reasons to go without it. Because then I really want to do it the hard-hard-hard core way. Or maybe because I have configured my system, and want to freeze my code. And nothing prevents me to do it ‘my way’.
In any case, it is easy to transform a CodeWarrior Processor Expert project, and then decide to remove that technology from it, and go further with the ‘traditional’ technology.
USB has two sides: if it works, it is great :-). If it does not, it is really bad :-(. It took a while in the desktop and PC world until USB for common devices (mouse, keyboard, memory sticks, …) was working without issues. But ‘non-standard’ devices like a USB debugging probe/cable are not of that kind of category.
Occasionally I run into USB driver issues in my class. So this post is about identifying the different USB driver parts for the P&E OpenSDA, P&E OSBDM/OSJTAG and P&E Multilinks. And how to install the drivers manually if something is not going well.
Usually I compile my sources, link it and pass it to the debugger for downloading it to the target. And ‘downloading’ means for me: flashing to the target (RAM debugging is something for the non-hardcore programmers ;-)). But there are more options than only downloading and flashing. There is definitely more which helps me to do post-mortem (yes, I *love* Latin :cool:) debugging.
Downloading means to me that the debugger will program my application into the device, then loads the symbolics (debug information, source file information, …) and then I debug my application. Looking at the ‘Debug As’ options, there is as well Attach and Connect:
Debug as Attach, Connect and Download
Eclipse provides in the Editor view great tool tips (called ‘hovers’) which shows what is behind a macro: I can move my mouse over it, and it shows me the content behind it:
Macro Expansion Hover in Editor View
When I create a new bare-board project with the Eclipse based CodeWarrior 10.3 for my FRDM-KL25Z board and GNU gcc, then the ‘Library’ option is grayed out:
Library Option in New Project Wizard
This does *not* mean that libraries cannot be built :-). In fact it is very easy to do this with the GNU tools and Eclipse, and here is how….
Question: What to do on a rainy Sunday?
Answer: Having fun with USB and the KL25Z Freedom board! :-).
In “A shell for the Freedom board” I used the UART-to-USB OpenSDA capability of the KL25Z Freedom board: The KL25Z processor uses the OpenSDA K20 microprocessor as Serial-to-USB converter. But this only works because of the P&E OpenSDA USB CDC (Communication Device Class) implementation. If I create my board without OpenSDA, I need a different approach: I want to do USB CDC with the KL25Z :twisted:.
USB CDC Device on COM22
In this post I have found settings for Eclipse Indexer to show the state if defines correctly. Usually I have something like this in my projects:
debug me
So I define the macro DEBUG_ME on the compiler command line. And it is cool to see that the Eclipse editor correctly grays out the code which is not enabled. But for this the Eclipse Editor view needs to know about the macro, but how does this work?
The Kinetis-L is a 32bit microprocessor family, based on ARM Cortex M0+. It comes with ARM gcc in CodeWarrior. Although the Kinetis-L does not have much RAM, it is very possible to use gcc with C++, especially as a programmer I keep the limited RAM amount in mind. So I thought I try C++ and Processor Expert for my Kinetis-L KL25Z Freedom board.
If I select C++ as language in the New Bareboard Project Wizard of CodeWarrior, then I cannot select Processor Expert or Device Initialization:
C++ in the New Project Wizard
That makes somewhat sense, as Processor Expert creates normal C code and C files, but no C++. Still, what if I need C++? This is doable, but with anything advanced, I need to know exactly what I want and what I do. Here is the ‘How to use C++ with Processor Expert’.
MCU on Eclipse 