Tag Archives: arm gcc

Defining Variables at Absolute Addresses with gcc

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Many compilers offer a way to allocate a variable at an absolute address. For example for the Freescale S08 compiler, I can place my variable at a given address:

unsigned char buf[128]@0x2000;

This is very useful (and needed) e.g. if the hardware (like USB) needs a buffer at given address. The advantage of the above (non-ANSI and thus not portable) syntax is that I can define a variable at an absolute address, without the need to allocate it in the linker.

I wanted to do something similar with gcc for Kinetis/ARM, and searched many forums on the internet. Obviously, I’m not alone with this question. The solution I have found comes close to what I use e.g. for the S08 compiler.

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Copy my CodeWarrior Project

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I have a project working, and then I want to do a copy. Unfortunately, this is not as simple as it should be :-(. In order to copy a project with all the settings, some knowledge about the internals of the project structure is required, which is the topic of this post.

In “Copy my Project” I was using a ColdFire V2 project which is not an easy case, as is using a Target Task to flash the microcontroller. Fortunately, all other targets in CodeWarrior for MCU are *not* using target tasks :-). With little help and preparation, a copy a project is not that difficult to do.  I’m showing how to do this with the FRDM-KL25Z project I have created in this post.

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A Library with ARM gcc and Eclipse

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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

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….

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Tutorial: USB CDC with the KL25Z Freedom Board

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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

USB CDC Device on COM22

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Compiler Defines and Eclipse Editor Highlighting

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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

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?

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