here I have an avr development board with a core of type Atmega32u4. I can only access to the memory via a usb cable.The default fuse bits seem to enable the JTAG which I want to disable. Unfortunately, the lock bits only allow me to program the application section. Does anyone know how to change the fuse bits via the usb port in this case?
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Short answer: You can't. You must have some sort of in-circut programmer in order to change the fuse settings.
Brendan Simpson
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thanks. I finally changed the fuse bits via an ISP programmer – user125568 Jan 11 '17 at 13:04
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See the 32u4 datasheet and the AVR instruction set manual.
Programming the fuses can only be done via
- 28.6 Parallel Programming (pg. 359)
- 28.7 Serial Downloading (pg. 367)
- 28.9 Programming via the JTAG Interface (pg. 371)
Though the program may write to the flash memory (SPM instruction) the fuses can only be read via the ELPM instruction.
Details on reading the fuses in self-programming mode can be found in 27.7.9 Reading the Fuse and Lock Bits from Software.
try-catch-finally
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