ARDUINO MEGA 2560 REV3 Disable auto-reset

Hello everyone, surfing the net I read some articles that say that you can disable the auto reset of the arduino. I have not found anything about the ARDUINO MEGA 2560 REV3, can someone tell me if it is enough to put a 120 ohm resistor between the Reset and 5V or for this model there are other things to do? I'd like a confirmation before I go and ruin my card...
Goodbye, everyone :slight_smile:

i have a 10uF capactitor between GND & RST, that works.

Thank you so much for the immediate response, so just the capacitor is enough? I don't have to touch the code?

The only code that would affect the auto-reset is in the 16u4 chip being used as a USB to serial converter (or whatever chip is being used in its place on a clone board).

Why do you need to disable auto-reset?

The official Arduino Mega board has a jumper labeled RESET-EN that can be cut to disable auto-reset, this may or may not be present on clone boards. When auto-reset is disabled, you will have to press the RESET switch manually when uploading code to the board.

so just the capacitor is enough? I don't have to touch the code?

Yes just a capacitor is enough, keep in mind if you want to upload a sketch you will either need to do a manual reset, or disconnect either end of the capacitor.

Why do you need to disable auto-reset?

I can think of a few reasons, just to be able to open the Serial monitor without resetting can be handy at times.

Deva_Rishi:
I can think of a few reasons, just to be able to open the Serial monitor without resetting can be handy at times.

Just wanted to make sure it wasn't something in their code that was crashing and causing an apparent reset, especially since they asked "I don't have to touch the code?".

Thanks a lot to everyone for the answers, I have to disable the auto-reset because I use the Arduino connected with a Raspberry and to avoid having to always leave the serial open I thought to disable the Arduino auto-reset function every time I open the serial.I have just one thing that is not very clear to me, I saw on the internet that use different values for capacitors, some use the 22uf ones, others the 10uf ones. I have 220uf at home, and a problem if I use those? What are the criteria to choose the capacitor?

Here are options:

  1. Genuine Arduinos have RESET-EN pads connected with path. You can cut this path to disable auto reset.
  2. Big capacitor ~10uF between RESET and GND. It should work from about 1uF and above but with 10uF it is more sure. Any bigger value than 10uF is good. This is probably the most used way.
  3. Small resistor between RESET and VCC, smaller than 1kOhm should work.

Perfect so my 220uf is fine since it's over 10uf. In a few hours I'm going to try to see if the 220uf capacitor is ok and I'll publish the result. Thank you all very much for your helpfulness and professionalism :slight_smile:

Hello everyone, I confirm that the 220uF capacity works perfectly to disable the auto-reset and so I have solved my problem.Thank you all very much for your help.

You could also use a terminal program that does not issue a reset (does not activate the DTR line). Not sure what is available for the Raspberry Pi.