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Topic: Using empty UNO board to program external ATmega328 (Read 2 times) previous topic - next topic

Loudhvx


Can this technique be used to program an ATmega328 with a non-Uno bootloader?
For example, can I use an Uno board (minus microcontroller chip) as a USB-to-Serial programming interface for something like the Arduino Pro-Mini?  (The Pro-Mini board uses the ATmegaBOOT, whilst the Uno uses Optiboot, AFAIK)



I also used this method (empty UNO board to program ATmega328 chip) to program a 328 chip which had the older Duemilanove bootloader on it. The only difference in programming was that I had to choose "Duemilanove and ..." as the board type (even though the actual board was an UNO).

One difference in the bootloaders is that at power-up, the optiboot loaded chip starts the sketch instantly.  The Duemilanove-bootloaded chip waits one second.  However, both boards wait a second after a reset press, before running the sketch.


I'm not sure what a Pro-Mini is, exactly. But if it doesn't have the USB port, there may be a way to use the UNO to communicate with it. At least the bootloader difference shouldn't be an issue.

Loudhvx


Quote
If the UNO is unplugged from the computer, it has no power on it and tends to drag down the reset line, even with a 10k pull up on the Atmega328's reset pin


That's possibly solvable by adding a 100nF in series, so that only fast downwards edges pull it down.

Thanks for the heads-up.

markp912

i am new to the whole arduino controller, but so far i enjoy it. So i can remove my ATmega328 from the UNO board and put it onto a bread board with my program loaded onto it and add the crsytal and two capacitors and have it work just like the UNO would work? Thank you

Coding Badly


Loudhvx

Yes, but I should add one note...

In one of the tutorials, it shows the Aref pin connected directly to 5v. You should not do that, it is dangerous. If you are not using the external reference for analog inputs, you should leave that pin unconnected. If you are using the external reference, you should use a 5k resistor to connect an external voltage to that pin. That will prevent the chip from burning in case the internal reference is selected accidentally in the sketch.

Look up the tutorial for external reference if you are going to use that feature.

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