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Topic: power supply problem on Arduino NG (Read 446 times) previous topic - next topic

brandon

I'm working with Arduino NG (ATMEGA168) and it works fine when suplying power via USB cable. But when I give external power supply the POWER led is on but nothing happens (the power selector jumper is changed to EXTernal, logically). Then, if I connect the USB cable (not power, just for data) it starts the program. I can unplug the USB at any moment and the program continues perfectly, but if I press the reset button it won't start until I plug the USB again.

┬┐Why is this happening and more important, how can I make it work without the use of a USB cable?

Thanks

Triffid Hunter

sounds like the ft232r is holding reset low. I think that's why they replaced the resistor from DTR to reset with a capacitor on the diecimila, and completely removed the one from RTS.

Adilson Akashi

#2
Apr 07, 2008, 04:23 am Last Edit: Apr 07, 2008, 04:28 am by adilson Reason: 1
I'm not sure, but I think it's an old problem, with many posts.

Try to put a 10k resistor from RX (pin0) to +5v. or to GND when not using USB cable.

Atmega RX pin keeps "floating" when not using USB, that makes Atmega think there is incoming data.

[edit]Found:
http://www.arduino.cc/en/Guide/Troubleshooting#toc1
[/edit]
PCB Designer

brandon

I've tried connecting RX to TX because I can't find a 10K resistor right now and it's working.  :)

Thank you very much.

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