SparkFun Forums

[pfarmer]

Hi All,

I started playing with an atmega32u4 breakout (Sparkfun) yesterday, and noticed that after a power cycle it didn't run my application (a simple blinky type app). So I did some googling and quickly came to the conclusion that BOOTRST was programmed, hfuse 0xd8, so set about trying to set hfuse to 0xd9, everytime I did it would fail.

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avrdude: verifying ...
avrdude: verification error, first mismatch at byte 0x0000
         0xd9 != 0xd8
avrdude: verification error; content mismatch

So after some more googling I discovered the lockbit, it was set to 0x94, so after some googling and reading the datasheet for the atmega32u4 I discovered I could reset the lockbit by erasing the chip, so I did this:

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avrdude -e -v -c avr109 -p atmega32u4 -P /dev/ttyACM1

Strangely after I'd done this (successfully according to avrdude) my app started running. The lockbit now tells me its set to 0xC0:

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>>> dump lock 
0000  c0                                                |.               |

However if I try to write a new value into the lockbit I get this (I know this won't work):

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avrdude> write lock 0 0x97
>>> write lock 0 0x97 
avrdude (write): error writing 0x97 at 0x00000 cell=0x94

Interestingly the lockbit claims its 0x94, and it will allow me to write 0x94 into it.

The current status of my board is that it boots into the bootloader, I then need to perform some function with avrdude to get it run my blinky code, but I can't write any new code to it.

Am I missing something here? How can I force the chip to actually erase resetting the lockbit.

avrdude version: 5.11.1

Thanks,

Peter

[pfarmer]

Fixed it, programmed an UNO as an ISP.