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I am working on a home made project,where i am using Atmega2560V-8AU (note the suffix, this part has an 8 MHz maximum clock rate) as my main controller, supplying 3.3V to this chip.

I want this controller to work exactly same as standard Atmega2560-16AU like on Arduino Mega(perhaps at a slower baud rate on account of the slower clock)

Does there already exist a suitable bootloader image and board definition for an ATmega2560 operating from an 8 MHz crystal?

If not, what changes would need to be made to the usual 16 MHz bootloader and boards definition to support 8 MHz operation, both for the bootloader and for correct time functions and serial buad rates in sketches?

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  • @Gerben - how do you propose the lower clock speed be handled? If you are suggesting there is already an option for it, mentioning that would be clearer.
    – Chris Stratton
    Jun 9, 2017 at 15:35
  • @Gerben - you seem to be ignoring the whole point of the question - the poster wants to use an atypical chip which cannot operate at the normal clock rate. It either needs a custom bootloader to operate at a usual baud rate, or programming support for a slower baud rate. Your responses so far have been the exact opposite of helpful.
    – Chris Stratton
    Jun 9, 2017 at 15:57
  • In actual fact, the ordinary bootloader will work, but the problem will come when then trying to talk to it - it will be operating at half the expected baud rate due to the 8 MHz vs expected 16 MHz clock, so the usual board definitions won't allow the IDE to talk to it. What the poster needs is a good board definition package for an 8 MHz Arduino Mega.
    – Chris Stratton
    Jun 9, 2017 at 15:58
  • There is a fair amount of coverage here and elsewhere for 8 MHz / 3.3v usage of the ATMega328p - the situation with the 2560 will be similar enough that those solutions could be used as a model for the necessary modifications or workarounds, but of course an ATMega328p board package won't actually work on a 2560.
    – Chris Stratton
    Jun 9, 2017 at 16:05
  • Hello, I am sorry for not providing enough information my task! I am using 8Mhz crystal and the chip runs on 3.3V, I cannot upload bootloaders of Atmega2560-16AU which runs on 16Mhz cystal. Yes! the ordinary boorloaders should work! but i need to change 16Mhz set to 8Mhz set somewhere in some files of ARduino IDE How do i dot that.? and is there any more things i have to do like Fuses etc.? and I am using my Arduino UNO as "Arduino as ISP" programmer in the list, which will have +5V on the SPI lines and I am running my target chip on 3.3V, Does it hurts to my chip.? Thank you
    – Mudassir Hussain
    Jun 9, 2017 at 16:26

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I have used megacore bootloaders, and it solved the problem

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