the "fuses" target always erases flash for attiny85 (and others)

[liebman]

This is bad when your setting fuses to turn the reset pin to an IO pin. The '-e' option (erase) is included from two places: 1) The FUSESCMD uses UPLOADERFLAGS and from the board definition the upload.extra_flags are appended and for attint85 for example this includes -e. This happens in BeforeUpload. 2) The setup for the fuses target also adds the -e option here.

There is a work around using an extra script:

Import('env')

# the uplaod flags for attiny85 adds -e that erases the flash and when we don't
# want that to happen when we are setting the fuses, espically when we change
# the reset pin to an IO pin.  The '-e' is actually added twice, once via extra
# upload flags in the board definition and once in the setup for the fuses target
def fuses_command(source, target, env):
    env['UPLOADERFLAGS'].remove('-e')
    cmd = " ".join(
        ["avrdude", "$UPLOADERFLAGS"] +
        ["-U%s:w:%s:m" % (k, v)
        for k, v in env.BoardConfig().get("fuses", {}).items()]
    )
    return env.Execute(cmd)

env.Replace(FUSESCMD=fuses_command)

This is my platformio.ini:

[platformio]
default_envs = default

[env]
board = attiny85
platform = atmelavr@1.15.0
framework = arduino
build_flags = -D__AVR_ATtiny85__
board_build.f_cpu = 1000000L ; we run at 1Mhz
extra_scripts=fuses.py ; fix fuses target not to erase flash!

[env:default]
; fuses for 1Mhz/bod=1.8/EESAVE/RSTDISABLE
board_fuses.hfuse = 0x56
board_fuses.lfuse = 0x62

[env:testing]
; fuses for 1Mhz/bod=1.8/EESAVE
board_fuses.hfuse = 0xd6
board_fuses.lfuse = 0x62

[ngkz]

"extra_flags": "-e" also causes an issue that uploadeep target erases flash.