ATMEL HOWTO

Step 1: Installation

Step 2 (AVR Studio): Creating and compiling your program

See the AVRstudio discussion.

Common Problems

• text region full: Make sure the "optimization" flag is set (see above). You will probably also need to re-add "F_CPU"
• Oulib error: F_CPU not defined. Re-add "F_CPU" as above. After this, perform a "build clean" and a "rebuild all"
• Many things undefined, such as DDRB and PORTB. Re-set your device to "atmega8"

Step 2 (non-AVR Studio): Creating and compiling your program

• Create your C program (you can start with this sample program: led_flash.c). You will need a text editor of some form (e.g., xemacs)

• Create a makefile (start with this sample makefile)

• Grab a current version of OUlib: libou_atmega8.a and oulib.h and place it in your project directory (or place a shortcut to these files in your project directory). You may also want oulib_serial_buffered.h and buffer.h.

• Modify the makefile so that it points to your source file:
  Change the TARGET = led_flash.c line so that it contains the name of your source file.

• Compile the your program:
  • Use your shell
  • Use the "cd" command to change directory to the location of your makefile and source file.

  • Type make. If there are no errors in your program, you will have a variety of files, including:
    • led_flash.lss: a file that shows both your program and the corresponding assembly code
    • led_flash.hex: a file that contains the program information that will be downloaded to your processor

• From your program directory, type: make program
  • If you are using the AVRISP mkII (the blue cases), make sure that your port is set to usb

  • If you run into device permission problems, you can do this as root as a temporary measure (to configure for standard user use, you must configure udev properly)

• Setting the programmer frequency: (if you run into trouble)
  • Enter interactive mode:
    avrdude -c avrispmkII -P usb -p m8 -F -u -t

  • parms will give you the current clock period

  • sck [period] will set the clock period
    Use 1 for high speed programming (not possible unless you are using the external 16 MHz crystal)
    Use 10 for low speed programming (compatible with the internal clock)
  • quit

• Configuring for use with the external crystal: (again, use if you run into trouble)
  • Set programmer frequency for low speed programming (above)

  • Use make setfuse (make sure you have the latest copy of the makefile)

  • Set programmer frequency back to high speed programming

Step 3: A Basic Circuit

You may use the original led_flash2.fig file if you wish (this is an xfig file).

The key components are:

• The Atmel Mega8: your microcontroller. Note the power and ground connections.
• The AVR ISP Connector: connects the processor to the programmer.
• L1 and L2: LEDs used in the sample program. Note that the polarity of the LEDs is critical. Also - you need a resistor in series with each of the LEDs (200-1K ohms will do).
• LC is a status LED that allows you to see when the programmer is downloading code to your processor. This LED is useful, but not necessary.
• The crystal and 15 pF capacitors (these can also be 18 pF) connected to pins 9 and 10 are necessary if you want your processor to be clocked at 16 MHz (by default the processors use an internal clock that runs at 1 MHz).
• The 10K ohm resistor on the reset line (pin 1) keeps the line high so that the processor will not reset (unless commanded by the AVR ISP programmer).

Hints

• It is always a good idea to flash an LED in some unique way at the beginning of your program. This way, you can be sure that your processor is receiving power and that the power supply is stable.

• You can find other examples in the examples directory.

• You can also download the oulib source and examples: oulib_2010_02_11.tar.

• AVR Freaks has a tutorial on bit manipulation in C

• Suha has a tutorial on manipulating ports on the Atmel (note that this is a slightly different processor than the mega8, but the principles are the same).

Atmel Mega8 Details

• Full Atmel Mega8 Manual

• AVR ISP Userguide (first 3 chapters are useful)

• AVRDude Userguide (Note: this copy is old)

• AVR Lib Manual. You may find the AVR Lib Manual in PDF more useful (this is also an old copy).

• OUlib Module Documentation

fagg [[at]] cs.ou.edu

Last modified: Tue Feb 15 00:53:42 2011