Program 8mhz into 328
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Program 8mhz into 328

by sydkahn on Fri Feb 24, 2012 6:42 am

I want to make a low power blinky project using a 328 and batteries. I keep reading about setting fuses. I read somewhere on here (i can't find it now) that all you have to is select an 8mhz board from the arduino drop down list and burn its boot loader. Is this true? It can't be that easy.

I'll assume that then i do not need to use a crystal (or resonator) and that the 328 will run as an arduino on its internal osc.
Will i have to trim up the internal osc to get the boodloader to recognize the serial programming. Or will i have to continue to use the isp.
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Re: Program 8mhz into 328

by philba on Fri Feb 24, 2012 1:58 pm

Well, Atmel calls it a "precision" oscillator so hopefully it will be ok. Generally, at room temperature it will probably work fine. They have to qualify their components across a braod temperature and voltage range so they are going to be conservative on their claims. I'd just try it and see what happens.
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Re: Program 8mhz into 328

by westfw on Fri Feb 24, 2012 8:11 pm

Will i have to trim up the internal osc to get the boodloader to recognize the serial programming.

The internal oscillator only runs at 8MHz, which doesn't quite support 115200. So you can either program a new bootloader modified for 8MHz and 57600bps, OR you can use the standard 16MHz bootloader at 8MHz by configuring boards.txt to run at 57600 instead of 115200.

The oscillator is "precision" when calibrated. It should be good enough for serial communications, but it would be chancy if the calibration byte were erased or misconfigured.
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