Arduino Duemilanove resets frequently on USB power

Hello,

I've got a couple of Duemilanoves which I use for quick prototyping and testing. Bigger and/or more complex projects are moved to separate breadboards with standalone Atmega368P-chip and separate powersupply.

But, I'm experiencing that the Duemilanove resets the microcontroller frequently(every third og fourth second). This only happens when it is connected to USB(Arduino software does not need to run on computer). If I power the Duemilanove with 9-12v it works perfectly.

Any suggestions?

It depends on your USB port. The FTDI tells it to deliver 500mA, but sometimes it can't...

To check just connect an USB hub, the very cheap ones sometimes even ignore this limitation.

Unlikely, but the FTDI could have been reprogrammed (using FT_PROG, formerly MPROG) , also with respect to the current request parameter... http://www.ftdichip.com/Support/Utilities.htm#FT_Prog

I don't think it is a lack of current issue. The latest cirquit consisted of three LEDs and a thermistor.

Update: Actually I just discovered that the same thing happens on my breadboard when I have my FTDI-board connected to the Arduino chip, with reset connected to the DTR pin. The breadboard is connected to a separate powersupply, and 5v + GND from the FTDI are left disconnected. If I remove the DTR pin from reset it works perfectly.

Strange.

Maybe strange... So someone it toggling the DTR.... Please check if the problem also occurs when the port is in use (just open the Serial Monitor Window and wait).

It can not be a hardware defect on the PC, as DTR is as "software signal" with virtual ports. It cannot be a problem with the FTDI chip, as it happens to all of your boards.

You misunderstood me - I did not want to say that you are spending to much current, but that the (defective?) USB port can be delivering too little. If this is only 50mA ,and fluctuating , rather than 500, the symptons would be similar.

If I remove the DTR pin from reset it works perfectly.

Sometimes this symptom can be cause by some software application on the PC that is scanning for available comm ports. Things like cell phone, camera, and other background application that use comm ports. You might try turning off suspect PC applications and see if the symptom goes away.

Lefty

Solved! The problem was, as retrolefty suggested, Sony Ericsson PC Companion :)

deSilva: Sorry. I misunderstood you. :)

Thanks for the help both of you!