EE 281 Lab 1: Using AVR GCC

These instructions are for installing the AVR GCC compiler and libraries on a Windows 2000/NT system.  More information about this can be obtained at the following link: http://www.avrfreaks.net/AVRGCC/.  For information about installing AVR GCC for Linux, follow this link: http://combio.de/avr/

1. Setting up the compiler:
• Downloading the files  You can get the compiler and library files here:  avrgcc20011121a.exe. You also need to download the GCCTEST files gcctest.zip.  This contains not only good sample code, but also contains a predefined setup of makefiles which make compilation much easier.  
• Installing the compiler:  Simply double-click on the executable to install the files.  By default, all components should be selected for install and the destination directory will be C:\avrgcc (I would strongly recommend leaving things this way).  When the executable runs, all the files will be copied over to the destination directory and also all of the library files will be compiled for you.  
• Setting up environment variables for Windows 2000:   If you are running Windows 2000 you will need to set some environment variable settings to enable you to use avrgcc from any dos prompt. (Remember to remove these settings if you are reinstalling/upgrading. Or else the recompiling of the library files may fail.)  The environment settings can be found in the file: C:\avrgcc\run.bat and probably look like this: (Replace C:\avrgcc with the path where you installed avrgcc.)
    set AVR=C:\avrgcc
  set CC=avr-gcc
  set PATH=C:\avrgcc\bin;%path%
  To add these changes in Windows 2000, right-click on My Computer select Properties.  Select the Advanced tab and and click on the Environment Variables button.  You will need to do the following three things in this window:  1) Under the User variables for (username) section, find the path variable and click on Edit to bring up an Edit User Variable box.  You will need to add the following to the end of the Variable Value field:
  ;C:\avrgcc\bin
  Make sure that no spaces are added before the semicolon, otherwise this will not work.  When you are done, click on OK for the Edit User Variable box.  2) Next, click on the New button to add a new environment variable.   In the Variable Name field, add the name AVR,  then in the Variable Value field add the value C:\avrgcc . 3) Similarly, create one more environment variable named CC and set its value to avr-gcc . Once you have done this, click the OK button in the Environment Variables window.  
• Setting up environment variables for Windows 98:   If you are running Windows 98 you should be able to simply double-click the icon that was added to your desktop or Start Menu during the install process. If you still have problems with this (such as make not being recognized as a valid command or io.h not being found) you may need to make some additional changes.  (Remember to remove these settings if you are reinstalling/upgrading. Or else the recompiling of the library files may fail.)  The environment settings can be found in the file: C:\avrgcc\run.bat and they probably look like this: (Replace C:\avrgcc with the path where you installed avrgcc.)
    set AVR=C:\avrgcc
  set CC=avr-gcc
  set PATH=C:\avrgcc\bin;%path%
  You can cut and paste these into your autoexec.bat file, but you may need to make one small change first. Depending on your system, you may have spaces in your path string (example: …;c:\Program Files\…) and these spaces may cause this string to get parsed as two strings instead of one. This problem should be fixable by placing quotes around %path% before copying it into autoexec.bat:
   set PATH=C:\avrgcc\bin;”%path%”
  You should probably add these quotes in both the autoexec.bat and the run.bat files. Once this is done and autoexec.bat has been run, any command prompt should be able to correctly call make (c:\avrgcc\bin\make.exe).
• Installing GCCTEST:   Extract the gcctest.zip file to your C:\avrgcc directory.  You will need to copy the make1 and make2 files from the C:\avrgcc\gcctest\include directory into the C:\avrgcc\include directory. These files are needed in order to use the makefiles in each of the gcctest1-gcctest9 directories.  

2. Compiling GCCTEST projects:

The GCCTEST files give 9 very good examples of C code written for the AVR. Each of these can be compiled and downloaded to your STK500.  We strongly encourage you to look through these examples to get a feel for how to use C with the AVR.   Here is a description of how to compile these projects.

• Bring up a Command Prompt: Change directory to one of the gcctestx directories (example: c:\avrgcc\gcctest1\).
• Compiling: Once in the proper directory, all you need to do is type 'make' to run the compiler.  The make command will run the compiler using the makefile that is in the current directory.  If the compilation is successful, "Errors: none" should be the last line of the 'make output.  The gcctest examples already have makefiles made.  Below is information on how to set these up for your own projects:
• Setting up makefile: The best way to create a new makefile for your project is to mimic one of the makefiles in the gcctest examples.  (If you need an example that uses multiple source files, use gcctest7).  If you copy a makefile from one of these gcctest examples, then you will be able to leave most of the lines of the makefile unchanged.  The only lines that you will probably need to change are the MCU (to match the processor you are using), TRG (to change the name of the target file, which usually matches your .c file), SRC (if you have multiple C sources), ASRC (if you have assembly files you want to link with your C code).  You will also need to change the dependencies if you have multiple source files.  The rest is handled by the makefile itself and the two files that you copied from the c:\avrgcc\gcctest\include directory (make1 and make2).
• Downloading to the STK500: This will be exactly the same procedure as for the other labs except that the file extension used by compiler is .rom instead of .hex. You can load this .rom file from within AVR Studio using the STK500 programming tool.

3. Other hints/suggestions:
• Use an editor with syntax highlighting: It will make it easier to read your code if you have an editor that performs syntax highlighting of C.  The simplest option for doing this would be to use AVR Studio, since you already have it.  Other choices such as Visual Studio or emacs would also be useful.

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Last modified: Mon Oct 22 12:19:03 PDT 2001