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Topic: Little help with bootloading? (Read 303 times) previous topic - next topic

RobDrizzle

Feb 02, 2012, 04:59 pm Last Edit: Feb 02, 2012, 07:16 pm by RobDrizzle Reason: 1
Hello all,
   I'm starting a project in which I would like to run a Atmega328P at 8MHz (or below) and at 3.3v to lengthen battery life. I'm going to have boards I designed spun in order to keep project costs down to a minimum as I will need ten of them and buying Arduino Pro minis at $20 will add up very quickly.

I'm having a good deal of trouble wrapping my mind around what has to happen in order to have success. Please bear with me as this is the first time doing any of this. I have a few items I would love to have cleared up and any help would be GREATLY appreciated.

What I plan to buy:
I want to buy the MCUs blank (I don't see the need to buy bootloaded chips when I'm going to change the parameters anyway).
I'm buying an usb ISP programmer, most likely the ATtinyISP from Adafruit.
All the chips will have an external 8.0MHz crystal and a 3.3v reg

What I have:
FTDI friend for sketch uploading
Arduino IDE 22 & 1.0

Questions:
1) Can I simply choose the Arduino pro mini 8MHz, 3.3v in "boards" and burn that bootloader with the ISP? Or will I have to mess with the fuses and set the brownout levels still?
2) Can this be done using my Arduino Uno board by placing the blank MCU in place of the existing and connecting the ISP. (I read a few times that you can not do this with a Uno and want to know if this has changed or is still true). Will the 20MHz crystal on the Uno prevent this from working?
3) Does anybody know if they fixed WinAVR so that is does not mess with the default Windows 7 paths. I have a 64bit machine FWIW.
4) Does/can the "Boards.txt" file write the fuses during a sketch upload or only when programmed through an ISP? I don't really understand what the "Boards.txt" file does. Any clarification on this would be great!

From my understanding, in order to get these puppies to work I will have to:
1) Either swap the MCUs on the Uno OR breadboard the MCU and wire (per one of the many guides) so that I can power the chip and use the ISP.
1b) Program fuses with ISP and WinAVR??
1c) Modify Boards.txt to reflect new settings??
2) Select and burn the Pro Mini 3.3v, 8MHz bootloader
3) Use the FTDI friend to upload my sketch
4) Success?!


Please let me know if I got anything or all of it wrong or if there is an easier more straightforward way!

Thank you.

kf2qd

You don't need to buy a programmer - you Arduino can do that function - The ArduinoISP sketch on your Arduino board, mount yur new chip on a breadboard with your crystal/resonator, 6 wires from your arduino board to your breadboarded chip, a 120 ohm resistor from +5 to reset on your Arduino board. I made a little board that looks like this -

RobDrizzle

Great information. I get to cross a questions off the list!

Thanks

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