dragon_notes

These are my notes on using an AVR dragon on Linux.

Right now it's mainly for an Arduino Pro Mini (so a Atmega328p), but if I use other devices I will update my notes.

We will use:

• AVR-GCC to compile the program
• AVRdude to upload the program and to set the fuses on the ATmega
• Avarice to debug
• AVR-GDB as interface to Avarice

I'm not really sure how the tasks are divided between Avarice and AVR-GDB, but I use them together.

The compile commands where taken from the makefile from the book "MAKE: AVR Programming".

Permissions for AVR dragon

You could run all upload commands using sudo, but that is not a good idea.

Better is to add a rules file. Add 99-avrdragon.rules to:

/etc/udev/rules.d/

and add yourself to the plugdev group using:

# groupadd plugdev
# usermod -a -G plugdev myusername

If the user doesn't exist yet:

# useradd -G plugdev myusername

The easiest way to apply these settings is to restart.

Arduino Pro Mini

Connections

What to connect on the dragon to the arduino:

• VCC (on dragon) - Arduino RAW
• GND (on dragon) - Arduino GND
• ISP pin 1 (MISO) - Arduino Pin 12
• ISP pin 2 (VTG) - Arduino VCC
• ISP pin 3 (SCK) - Arduino Pin 13
• ISP pin 4 (MOSI) - Arduino Pin 11
• ISP pin 5 (RESET) - Arduino RST
• ISP pin 6 (GND) - GND header on AVR dragon

Of course, we use a USB cable to connect the AVR dragon to the computer.

For my test setup nothing else is connected.

Fuses

We use avrdude to set fuses.

To read fuses, use:

avrdude -c dragon_isp -p atmega328p -nv

To set the default fuses, use:

avrdude -c dragon_isp -p atmega328p \
                -U lfuse:w:0xFF:m -U hfuse:w:0xDA:m -U efuse:w:0x05:m

These are the default fuses I got on my chinese Arduino clone. Check for yourself what they should be.

Compile

I've included a sample program, example_pro_mini.c

avr-gcc -Os -g -std=gnu99 -Wall -funsigned-char -funsigned-bitfields -fpack-struct -fshort-enums -ffunction-sections -fdata-sections -DF_CPU=16000000UL -DBAUD=9600UL -mmcu=atmega328p -c -o example_pro_mini.o example_pro_mini.c
avr-gcc -Wl,-Map,example_pro_mini.map  -Wl,--gc-sections  -mmcu=atmega328p example_pro_mini.o  -o example_pro_mini.elf
avr-objcopy -j .text -j .data -O ihex example_pro_mini.elf example_pro_mini.hex

Upload

avrdude -c dragon_isp -p atmega328p  -U flash:w:example_pro_mini.hex

Debug

This device only supports debugwire. To turn this on you need to set the right fuse. Check the datasheet for which fuse.

On the Atmega328p the fuce is bit 7 of the High fuse byte. Making something 0 turns it on, so if the byte was 0xDA and you want to turn debug on it will need to become 0x9A.

avrdude -c dragon_isp -p atmega328p -U hfuse:w:0x9A:m

Now it's ready for debug. Start avarice.

avarice --file example_pro_mini.hex -g -w :23232

and in a different terminal

avr-gdb example_pro_mini.elf
(gdb) target remote localhost:23232

Now you can debug. For example:

(gdb) continue

Will run the program. To stop it use CTRL-C.

(gdb) set delaytime = 40.0
(gdb) continue

And enjoy the fast flashing lights.

I had some problems with avarice (turns out I was using gdb instead of avr-gdb), and I got a segfault. My CPU usage was extremely high afterwards, and it turned out I had to kill it again.

ATTINY85

Connections

• VCC (on dragon) - ATTINY pin 8 (VCC)
• GND (on dragon) - ATTINY pin 4 (GND)
• ISP pin 1 (MISO) - ATTINY pin 6 (MISO)
• ISP pin 2 (VTG) - VCC header on AVR dragon
• ISP pin 3 (SCK) - ATTINY pin 7 (SCK)
• ISP pin 4 (MOSI) - ATTINY pin 5 (MOSI)
• ISP pin 5 (RESET) - ATTINY pin 1 (RESET)
• ISP pin 6 (GND) - GND header on AVR dragon

Fuses

To read fuses, use:

avrdude -c dragon_isp -p t85 -nvB4

To set the default fuses use:

avrdude -c dragon_isp -p t85 -B4 \
                -U lfuse:w:0x62:m -U hfuse:w:0xDF:m -U efuse:w:0xFF:m

ATMEGA328P

Connections

• VCC (on dragon) - ATMEGA pin 7 (VCC)
• GND (on dragon) - ATMEGA pin 8 (GND)
• ISP pin 1 (MISO) - ATMEGA pin 18 (MISO)
• ISP pin 2 (VTG) - VCC header on AVR dragon
• ISP pin 3 (SCK) - ATMEGA pin 19 (SCK)
• ISP pin 4 (MOSI) - ATMEGA pin 17 (MOSI)
• ISP pin 5 (RESET) - ATMEGA pin 1 (RESET)
• ISP pin 6 (GND) - GND header on AVR dragon

Fuses

To read fuses, use:

avrdude -c dragon_isp -p m328 -nv

To set the default fuses use:

avrdude -c dragon_isp -p m328p \
                -U lfuse:w:0x62:m -U hfuse:w:0xD9:m -U efuse:w:0xFF:m