CDK4AVR HOWTO for Fedora 6

This is a HOWTO detailing my experiences with setting up the AVR cross-compiler tools under Fedora 6 using the cdk4avr suite. These tools are available in source form and in binary form for the i586 architecture. If you have a 64 bit PC then you can still use most of the tools by installing the binaries. Good luck with compilation. It is no doubt possible but under Fedora you will need to do some work. I may add this later if I find some enthusiasm for it.

Installation

When installing the rpms, the software is placed in /opt/cdk4avr. Note that there are no docs or man pages provided in the basic packages and these must be accessed separately. Obtain the following i586.rpms through the cdk4avr home page, which has a description and status given for each package.

cdk-avr-base. When you install this, it runs a script to set the environment. Logout and back in again to refresh the environment so that the command path is added to the PATH variable.
cdk-avr-binutils. Various utilities needed to convert file formats and including the GNU assembler and linker.

cdk-avr-binutils-doc-print. Contains a pdf manual.

cdk-avr-gcc. GNU compiler collection with C and C++. There is a separate package for C++.

cdk-avr-gcc-doc-print. Contains a pdf manual.

cdk-avr-libc. A subset of the standard C library for the AVR 8-bit microcontrollers.

cdk-avr-libc-doc-pdf. Alternatively from the avr-libc site get the latest pdf manual and man pages. Untar the man pages and copy man3 to /opt/cdk4avr/man.

cdk-avr-gdb. GNU debugger.

cdk-avr-gdb-doc-print. Contains a pdf manual.

cdk-avr-simulavr. A simulator for the AVR microcontrollers.

cdk-avr-simulavr-doc-print. Contains a pdf manual

cdk-avr-avrdude. Downloading and uploading the on-chip memories of AVR microcontrollers. It can program the Flash and EEPROM, and program fuse and lock bits.
cdk-avr-avrdude-doc-man.

cdk-avr-uisp.Downloading and uploading the on-chip memories of AVR microcontrollers. It can program the Flash and EEPROM, and program fuse and lock bits. This package is marked as obsoleted and so may gradually lag behind avrdude in terms of supported devices. However it has some small advantages over avrdude in regard to access to fuse and lock bits.

cdk-avr-tools. This package has some useful stuff but is not essential. There are a number of package dependencies that need to be tracked down. If using a 64 bit PC you will need to compile a lot of the packages to be able to use this.

Compilation of AVR Programs

There is some valuable information given in the Guido Socher article.

Test Compilation

Test the installation with a C program from the LinuxFocus site avrm8ledtest.c. For an ATMega8 MCU compile and link with:

$ avr-gcc -mmcu atmega8 avrm8ledtest.c -o avrm8ledtest.o

This will produce avrm8ledtest.o.

avr-gcc

A simple compile will perform both a compile and link process. The -c option will perform the compilation but will not link. This is necessary if there are additional external files to be linked.

Linking is done at the end of the process by taking all the object files as inputs and using avr-gcc again, eg

$ avr-gcc -mmcu=atmega8 -o uart.o uart.c

$ avr-gcc -mmcu=atmega8 -o acquisition.o acquisition.c

$ avr-gcc -mmcu=atmega8 -o acquisition.out uart.o acquisition.o

avr-objcopy

In order to produce a file suitable for uploading to the MCU. we need to convert it to a hex format. This command converts the output object file into such a format.

$ avr-objcopy -R .eeprom -O ihex avrm8ledtest.o avrm8ledtest.hex

This removes a section .eeprom and outputs in the ihex (Intel Hex) format.

Makefile

A sample makefile template written by Eric B. Weddington, J. G Wunsch, et al. can be used to compile multiple files. This just needs to be edited to add the MCU type and files to be compiled. Commands are:

$ make

$ make clean

$ make all

$ make program

The latter will download using avrdude. A make will compile to an object file, and create files for Flash and EPROM memory, so that the only command needed after a make would be to upload.

In the makefile template change the following lines for the avr-gcc compiler to suit your system:

-----------------------------------------------------------------------------------------------

# Change to whatever MCU you are using (check the avr-gcc documentation for the appropriate names)

MCU = atmega8

# Output format. (can be srec, ihex, binary)

FORMAT = ihex

# Optimization level, can be [0, 1, 2, 3, s]. 0 turns off optimization. s gives smallest code.

OPT = s

# Target file name (without extension).

TARGET = application

# List C source files here. (C dependencies are automatically generated.)

SRC = $(TARGET).c

-----------------------------------------------------------------------------------------------

Programming the Device

Avrdude is quite good and is currently being maintained. In the absence of a commercial programmer, the best interface to use if you have access to a parallel port is DAPA which is quite reliable. Avrdude can use some serial protocols, toggling certain lines to provide the reset and clock signals. These are DASA (appears to be unreliable) and DASA3 (unknown reliability). The Guido Socher article gives information about how to make a DAPA cable. I made one from an old Centronics printer cable that was passing by on its way to landfill. If you use a commercial programmer or cable, quite likely avrdude will support it.

The command line to use for our ATMega8 and DAPA cable is:

$ sudo avrdude -p m8 -c dapa -e -v -U flash:w:application.hex:a

The relevant command line parameters are:

-p is a code for the microcontroller. m8 is ATMega8. Check the man page.
-c is a code for the interface. This is the parallel DAPA interface.
-e erase the memory before programming.
-v verbose
-U has the parameter memory:operation:filename:format, where memory refers to the flash memory, w refers to write, and a refers to an autodetect format (it is a default and can be omitted).

Note that access to the parallel port requires root privileges, hence the sudo command. Many websites recommend changing the privileges on the /dev/parport0 device file but with udev now generating these device files on boot, such an operation would need to be repeated each time the PC is booted (unless you can convince udev to do it for you).

In the makefile template locate the program: section and modify it by adding the following to allow make program to work:

-----------------------------------------------------------------------------------------------

AVRDUDE_PROGRAMMER = dapa

AVRDUDE_FLAGS = -p $(MCU) -c $(AVRDUDE_PROGRAMMER) -v -e

AVRDUDE_WRITE_FLASH = -U flash:w:$(TARGET).hex

program: $(TARGET).hex $(TARGET).eep

sudo '$(AVRDUDE) $(AVRDUDE_FLAGS) $(AVRDUDE_WRITE_FLASH) $(AVRDUDE_WRITE_EEPROM)'

-----------------------------------------------------------------------------------------------

Fuse Bits

These are device configuration settings in the microcontroller that are not affected by flash memory erases and so persist over time. They must be deliberately set or reset with a special command. They control certain hardware options for the microcontroller operation. Note that carelessness in programming these has the potential to render the device useless.

To display the settings, uisp is the best tool if it supports the device (avrdude can do it but less transparently). If using the DAPA programmer and the ATMega8, the following command will show the fuse bits neatly in hex format. The output for the default settings follows:

$ sudo uisp -dprog=dapa -dpart=atmega8 --rd_fuses

Fuse Low Byte      = 0xe1
Fuse High Byte     = 0xd9
Fuse Extended Byte = 0xff
Calibration Byte 0 = 0xb5 (Read Only, for more calibration bytes use --rd_cal)
Lock Bits          = 0xff

To reprogram the fuses, avrdude can be used. To change the ATMega8 clock source from the default internal 1MHz clock to an external 8MHz crystal, we use the following command. Again, take care and double check everything before proceeding.

$ sudo avrdude -c dapa -p m8 -U lfuse:w:0xEF:m

Extended Fuse Problem

Having managed to destroy all my ATMega8 chips I moved on to the cheaper and more capable ATMega88 with its brothers ATMega48 (4M Flash) and ATMega168 (16M Flash). Here there arose a small problem with both avrdude and uisp. The extended fuse byte in uisp was not accessible to uisp and avrdude barfed over it, returning a failure indication and an invalid read back after attempts to program it. The problem with uisp was that the source code did not include the extended fuse bit.

To fix this, delete the original uisp package. Download the uisp latest source uisp-20050207 (if the date is later than this, then the problem may have been fixed). Unpack into a suitable directory and enter the src subdirectory. Edit the Avr.C file. At the top there is a data structure for all the AVR devices. Find both the ATMega48 and ATMega88 entries. At the end of the entries replace the AVR_M163 with AVR_M128. Then save and return to the top directory. Execute the famous trio:

$ ./configure
$ make
$ sudo make install

The binary is installed by default in /usr/local/bin; either change the install location in the configure command or make sure your path points to it. At that point uisp was able to read and set the extended fuse. It appears that avrdude set the extended fuse correctly but couldn't read it back. I have been using cdk-avr-avrdude-5.1cvs-20060624.i586.rpm that was grabbed from some unknown location. The version available from Sourceforge is slightly earlier and was not able to deal with the ATMega88 at all, being unable to read the signature bytes.