I am playing around with the new avrlib-c 1.6.1 feature that makes it possible to specify fuse settings in the source code.
The idea is to make use of this feature from within a project's Makefile under Linux (and later to do the same for lock bits). I want to do it in two steps:
1) Have a script that extracts the fuse data from an .elf file and generates an avrdude command line from that data
2) Call the above script from within a Makefile target.
I couldn't find much documentation about the feature's implementation details, only what is in the avrlib-c documentation. So I'd like to check if I am on the right track with the following script.
out2dude-fuse:
#!/bin/bash
#
# Extracts information from .fuse section in elf
# binaries and generates corresponding avrdude
# command to set, get, or verify these fuse settings.
#
OBJDUMP=avr-objdump
FUSE_SECTION=.fuse
dude=avrdude
dudeopt=""
dudemode="w"
file="a.out"
MyName=$(basename "$0")
usage() {
cat <<!
usage: $MyName [-Wd ]* [-m ] [-p ] []
!
}
while [ $# -gt 0 ] ; do
case "$1" in
-Wd) [ $# -lt 2 ] && { usage; exit 1; }
dudeopt="$dudeopt $2"
shift
;;
-m) [ $# -lt 2 ] && { usage; exit 1; }
dudemode="$2"
shift
;;
-p) [ $# -lt 2 ] && { usage; exit 1; }
dude="$2"
shift
;;
-h) usage
exit 0
;;
--) shift
break
;;
-*) usage
exit 1
;;
*) break
;;
esac
shift
done
[ $# -eq 1 ] && { file="$1"; shift; }
[ $# -ne 0 ] && { usage; exit 1; }
$OBJDUMP --full-contents --section=$FUSE_SECTION "$file" | \
awk -v "program=$dude" \
-v "options=$dudeopt" \
-v "mode=$dudemode" \
-v "file=$file" \
-v "myname=$MyName" \
'
/\.fuse:/ { p++; next }
p && /^ [0-9A-Fa-f]/ {
low = substr($2, 1, 2)
high = substr($2, 3, 2)
ext = substr($2, 5, 2)
exit
}
END {
if(low == "") {
out = "echo \"" myname ": " file ": no fuse data found.\"; exit 0"
} else {
out = program " " options
if(high == "") {
out = out " -U fuse:" mode ":0x" low ":m"
} else {
out = out " -U lfuse:" mode ":0x" low ":m -U hfuse:" mode ":0x" high ":m"
if(ext != "") {
out = out " -U efuse:" mode ":0x" ext ":m"
}
}
}
print out
print myname ": command assembled: " out > "/dev/stderr"
}
'
#
For those unfamiliar with awk, I check for the start of the .fuse section. Inside the section I ignore the section address. I split the data into a maximum of three parts: First byte the low fuse (or just the fuse) byte, second byte (if any) the high fuse byte, third data byte (if any) the extended fuse byte. I verified this order empirically, but I'd like to get some confirmation that this is how things are done.
And here is a fragment of a makefile, showing how I gonna call the script:
OUT2DUDE_FUSE=out2dude-fuse
program-fuse: $(TARGET).elf
exec $$($(OUT2DUDE_FUSE) -p $(AVRDUDE) -Wd "$(AVRDUDE_BASIC) $(AVRDUDE_VERBOSE)" $(TARGET).elf)
.PHONY: program-fuse
