GDB + debugWire + Linux

gistfile1.md

gdb + avarice + debugwire on attiny88

enable debugwire

enable with avrdude (fuse for attiny88):

avrdude -c dragon_isp -P usb -p attiny88 -v -U hfuse:w:0xd9:m

compilation

• must be compiled with -ggdb or great (--gdb3) but doesn't seem to help with macros

• no optimisations

  COMPILE = $(GCC_PATH) -ggdb3 -Wall -Wextra $(OPTIMIZATION) -std=gnu11 -flto -mmcu=$(DEVICE) -DF_CPU=$(CLOCK)

need main.hex and main.elf

debugging

start avarice:

make && avarice -g -w  -P attiny88 --program --file main.elf :4242 -r

minimum required

avarice -g -w -P attiny88 :4242

then start gdb:

avr-gdb main.elf

and connect:

target remote localhost:4242

gdb useful commands

• list
• until main.c:23 # continue till this line
• continue
• print loops
• p/x loops # print in hex
• p/t loops # print in binary
• step
• set $pc += 2 # jump an instruction to get out of breakpoint
• layout # change different layouts
• x/t 0x2B # examine address in memory

breakpoints

only sw breakpoints with debugwire, so if need breakpoints use:

asm('break');

switch back to spi/icsp mode

NB. VTG/VCC pin (2 on header) must be connected to chip supply for this to work!

avrdude -c dragon_isp -P usb -p attiny88 -v

to disable debugwire on attiny88

avrdude -c dragon_isp -P usb -p attiny88 -v -U hfuse:w:0xdd:m

unresolved problems

• after breaking, can't conitnue without setting $pc (skip to next instruction: set $pc += 2)
• macros aren't defined

sources

• http://blag.pseudoberries.com/post/16374999524/avr-debugwire-on-linux
• http://www.homebuilthardware.com/index.php/avr/linux-avrdragon-tutorial-1/
• http://www.engbedded.com/fusecalc/