Some target devices need extra avrdude command line switches to
get them to upload successfully. There are dozens of options which
may be useful to different people. Instead of breaking all the possible
options out into separate fields, provide a generic "Program Flags" text
field which the user can fill in similar to the CFLAGS and LDFLAGS
settings.
The Arduino Mega2560 bootloader was changed[1] to report an error when
asked to erase flash because it has never actually implemented erasing
flash. To program this bootloader with avrdude requires the -D switch
to avoid flash erase. But it seems that every arduino will work fine
with -D, as evidenced by the fact that the Arduino IDE always [2]
includes -D in the avrdude commandline. Presumably the flash is erased
during/before programming anyway and the separate erase step is unneeded.
Perhaps the -D should be always added to avrdude command line in
configtool and in Makefile-AVR. But I haven't tested any other boards
yet, and I'm being more cautious even though the Arduino IDE does
otherwise.
[1] arduino/Arduino#543
[2] d8e5997328/app/src/processing/app/debug/AvrdudeUploader.java (L168)
90fbdd314a
