bootloader and -e command

[mcuee]

It seems to me that different bootloades deal with -e command differently.

One basic requirement is probably that a bootloader should not allow being erased, either by protecting the bootloader using lock bits (simple method) and by only erasing the other regions of the flash and not the bootloader region (better method).

1. stk500v2 wiring bootloader -- reject the -e command.

PS C:\work\avr\avrdude_test\avrdude_bin> .\avrdude.exe -c wiring -P COM3 -qqp m2560 -e
avrdude.exe: stk500v2_command(): command failed

2. avr109 -- accept -e command and will not erase itself (without lockbits change).
   And it seems to me -e is required in order to writie to flash. Initially I was not able to do that but with the tip from @MCUdude that I know I need to use -e. -D -U will fail to write to flash.

• [bug #51117] Problems with extended address (>128K) and buffer size #454 (comment)

3. optiboot -- using lockbits to protect and some may protect the bootloader, accept -e command. -e command is not necessary to write to flash. So -D -U command is okay.
   I am not so sure if this is always the case -- I tested with @MCUdude's MegaCore on the ATmega2560.

Update: some of the optiboot implementations may not be able to protect the bootloader once the lockbits are unlocked.

[mcuee]

An example from MightyCore from @MCUdude. You can see that the MightyCore optiboot bootloader are locked. Therefore -e works fine.

PS C:\work\avr\avrdude_test\avrdude_bin> .\avrdude -qqp m32a -c usbasp -U lfuse:r:-:h -U hfuse:r:-:h -U lock:r:-:h
0xbf
0xce
0xcf

PS C:\work\avr\avrdude_test\avrdude_bin> .\avrdude -qqp m32a -c arduino -P COM4 -e
PS C:\work\avr\avrdude_test\avrdude_bin> .\avrdude -qqp m32a -c usbasp -t
avrdude> d flash 0 0x100
>>> d flash 0 0x100
0000  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
0010  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
0020  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
0030  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
0040  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
0050  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
0060  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
0070  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
0080  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
0090  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
00a0  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
00b0  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
00c0  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
00d0  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
00e0  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
00f0  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|

avrdude> d flash 0x7e00 0x100
>>> d flash 0x7e00 0x100
7e00  01 c0 b2 c0 11 24 8f e5  98 e0 9e bf 8d bf 84 b7  |.....$..........|
7e10  88 23 61 f0 98 2f 9a 70  92 30 41 f0 81 ff 02 c0  |.#a../.p.0A.....|
7e20  97 ef 94 bf 28 2e 80 e0  ba d0 ea c0 85 e0 8e bd  |....(...........|
7e30  82 e0 8b b9 88 e1 8a b9  86 e8 80 bd 80 e1 89 b9  |................|
7e40  8e e0 ad d0 b8 9a 84 e0  20 e3 3c ef 44 e0 51 e0  |........ .<.D.Q.|
7e50  3d bd 2c bd 48 bf 08 b6  02 fe fd cf 98 b3 95 27  |=.,.H..........'|
7e60  98 bb a8 95 5f 99 02 c0  81 50 91 f7 91 d0 81 34  |...._....P.....4|
7e70  79 f4 8e d0 18 2f 97 d0  12 38 11 f4 80 e0 04 c0  |y..../...8......|
7e80  88 e0 11 38 09 f0 83 e0  7f d0 80 e1 7d d0 ee cf  |...8 .......}...|
7e90  82 34 19 f4 84 e1 8f d0  f8 cf 85 34 11 f4 85 e0  |.4.........4....|
7ea0  fa cf 85 35 41 f4 74 d0  c8 2f 72 d0 d8 2f cc 0f  |...5A.t../r../..|
7eb0  dd 1f 79 d0 ea cf 86 35  19 f4 84 e0 7c d0 de cf  |..y....5....|...|
7ec0  84 36 99 f5 65 d0 64 d0  18 2f 62 d0 d8 2e 01 2f  |.6..e.d../b..../|
7ed0  90 e6 e9 2e f1 2c 57 01  8f ef a8 1a b8 0a 58 d0  |.....,W...... X.|
7ee0  f7 01 80 83 01 50 75 01  b1 f7 5d d0 f5 e4 df 12  |.....Pu...].....|
7ef0  01 c0 ff cf 50 e0 40 e0  63 e0 ce 01 35 d0 7e 01  |....P.@.c...5.~.|

After I unlock the bootloader, -e is not really working properly as it will erase the bootloader.

PS C:\work\avr\avrdude_test\avrdude_bin> .\avrdude -qqp m32a -c usbasp -e
PS C:\work\avr\avrdude_test\avrdude_bin> .\avrdude -qqp m32a -c usbasp -U lfuse:r:-:h -U hfuse:r:-:h -U lock:r:-:h
0xbf
0xce
0xff

PS C:\work\avr\avrdude_test\avrdude_bin> .\avrdude -qqp m32a -c arduino -P COM4 -e
PS C:\work\avr\avrdude_test\avrdude_bin> .\avrdude -qqp m32a -c usbasp -t
avrdude> d flash 0x7e00 0x200
>>> d flash 0x7e00 0x200
7e00  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
7e10  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
7e20  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
7e30  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
7e40  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
7e50  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
7e60  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
7e70  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
7e80  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
7e90  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
7ea0  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
7eb0  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
7ec0  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
7ed0  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
7ee0  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
7ef0  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
7f00  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
7f10  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
7f20  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
7f30  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
7f40  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
7f50  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
7f60  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
7f70  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
7f80  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
7f90  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
7fa0  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
7fb0  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
7fc0  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
7fd0  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
7fe0  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
7ff0  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|