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Topic: Burning a sketch into a 328p with 8MHz bootloader in a 16MHz UNO board (Read 92 times) previous topic - next topic

MarkDH

I.e. my 328p is preprogrammed with 8MHz (external XTAL) bootloader.
I will put it in my standard 16MHz XTAL UNO board and try to load a sketch into it.
I think the baud rates will be wrong, but can the IDE be frigged somehow?
If not, then I understand how to program it on a breadboard using the ISP technique.
Cheers.

pylon

What do you mean by "8MHz (external XTAL) bootloader"? What bootloader is that (link to it)? You have to know the clock frequency to set the serial baud rates correctly.

Quote
If not, then I understand how to program it on a breadboard using the ISP technique.
Does that mean you have an ISP programmer?

hansibull

The Atmega328p is configured to use an 8 MHz external oscillator. When it's put into the Arduino UNO board, the clock frequency will be twice as fast, and you won't be able to upload your sketch using the USB to serial adapter on the Arduino UNO. However, you can use an ISP programmer.

What you can do is connect the ISP programmer, select the Arduino UNO option and hit "Burn bootloader". Now the microcontroller will be using a 16 MHz bootloader, and will work just fine with the "Arduino UNO" option.

If you want to use different clock frequencies, and still upload the code using the USB, you'll a separate core. I've created MiniCore, which is fairly popular. If you for instance want to use the internal 8 MHz oscillator, and get two extra IO pins to use, this is the option for you :)
MightyCore -  ATmega1284, mega644, mega324, mega164, mega32, mega16, mega8535
Github.com/MCUdude/MightyCore

MiniCore - ATmega8, mega48, mega88, mega168, mega328
Github.com/MCUdude/MiniCore

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