Arduino Forum

Forum 2005-2010 (read only) => Hardware => Troubleshooting => Topic started by: DrRossi on Jan 18, 2011, 10:39 pm

Title: Arduino Uno can't disable serial reset
Post by: DrRossi on Jan 18, 2011, 10:39 pm
I would like to disable the reset on serial communication on my Arduino Uno.

I follow the tips at : <thissite>/playground/Main/DisablingAutoResetOnSerialConnection

Doesn't work!

First I tried to disable the DTR reset in perl, see the end of the aformentioned page.  Does not work.  Maybe because I use Device::SerialPort under linux?

Then I tried the 120 ohm resistor trick as mentioned in the beginning of the page and that doesn't work either!

Are these issues well known?  Do these tricks only work on pre-Uno boards?  

What are my options now?  Removing the capacitor or SoftSerial?

Thanks for any help.  

Title: Re: Arduino Uno can't disable serial reset
Post by: cmiyc on Jan 19, 2011, 12:07 am
The Uno has a trace called "RESET-EN" that you can cut.  Then if you want to re-enable the auto-reset, you just solder bridge the connection back.
Title: Re: Arduino Uno can't disable serial reset
Post by: retrolefty on Jan 19, 2011, 12:43 am
Quote
Then I tried the 120 ohm resistor trick as mentioned in the beginning of the page and that doesn't work either!

Actually that is an interesting question. The 8u2 usb chip might have a lot more ummpp from it's DTR signal to the 328 reset pin then the FTDI USB chip did. It would take someone owning both boards to experiment and see if it effectively defeats the auto-reset function on the Uno. I don't so I can't.

Lefty
Title: Re: Arduino Uno can't disable serial reset
Post by: DrRossi on Jan 19, 2011, 08:50 pm
I seem to have solved it for the moment by adding a capacitor between the reset pin and the ground.  I figured that with the resistor keeping the reset line up, the added capacitor maybe add enough oomph to keep the line up.

It did. I used 220 uF as it was the only one I had laying around, but I expect that a much smaller capacitor works as well.

Thanks for the responses.