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Topic: please add a jumper to disable auto reset (Read 110828 times) previous topic - next topic


After adding the 150 Ohm resistor, I can't upload sketch to board...I have to disconnect the resistor. Any hint to avoid this?


Press the reset button immediately before starting the upload.


So with the resistor mod we come back to previuos versions without autoreset...uhm...I would have both features...autoreset is a smart feature that I'd miss it...

Was wondering if applyng the following mods to bootloader I can have autoreset only on at upload of sketch:




Jan 26, 2009, 02:50 pm Last Edit: Jan 26, 2009, 02:52 pm by dcb Reason: 1
I just use the resistor like a jumper.  Stick it in the pin sockets when I don't want auto reset, take it out when I do.

P.S., I said 110 ohms, not 150.  You have to be precise with the resistors here.


I haven't any 110R resistor but with 150R works fine too.


Ok, if it works it works, going below 110 ohms is the real concern.  

Did you wind up soldering it in or something?


As not said :-( At first upload of a new sketch mod not working...

Code: [Select]

avrdude: stk500_recv(): programmer is not responding

I press reset just before uploading but nothing to do.

Also tried with a 47R tied to 3.3V but nothing.

Any hint?



the point of the resistor is to prevent the arduino from auto-resetting.

if the arduino does not auto-reset, the bootloader will not get a chance to listen for a new sketch without very careful timing.

remove the resistor(s) if you want it to be easy to program.  put the resistor back when you want to connect to the arduino without resetting it.


now seems works but...with following sequence:

1. in arduino ide press upload icon
2. wait for 2..3 seconds
3. press reset button



there is no critical time to respect...also 4..5 sec. after pressing upload icon

it's fine to me..


My tuppence worth. The addition of a breakable track is very laudible but does not really address the problem your design feature creates for users. All is well provided users stick with the provided software. That software manages the DTR signal. Most other software packages don't so users are stumped.

Given it is a feature that will be used by a few I would strongly recommend that you produce the board with the track cut but solderable for the few that will want to use the auto reset feature.

Then the board will work flawlessly with most serial software and build on the excellent reputation you have.


Howdy all.

Im outputting a value over serial through PHP to a webpage. If refreshed to fast, the value shows as 0.

I had also noticed that using the serial port with out Arduino's included serial monitor causes arduino to reset.
However leaving the serial monitor open all the time, while being impractical anyways, it seems to intercept any data sent to the pc from arduino, so the php cant access it.

With it disabled, the data is sent to php, and works just fine, as long as its not refreshed to fast, i then googled my way to this thread.

Now the resistor suggestions between reset and 5v pin does not work for me.  The board still resets from php. However when the resistor jumper is attached im not able to upload sketches. So apparently its doing something, just not the intented function.

Did not have a 110, however tried 120, 130, and 150.

Niether of these resistors did anything.

The board is still being reset.

Any suggestions?


May 05, 2010, 03:21 pm Last Edit: May 05, 2010, 03:40 pm by adalgisio Reason: 1

If you are using phpSerial, please, avoid it...

I switched to Perl and now all works fine (without any hardware mods) simply by disabling DTR.

I have a script in Perl that "fetch" data from Arduino through serial, then I have a "wrapper" in PHP which catch the Perl result and save in a PHP variable.


P.S. Only an advice: when upload sketch be sure that fetcher.pl don't ask Arduino to send back data...otherwise the serial flow being stalled and you must kill the relative pid of fetcher.


May 05, 2010, 04:38 pm Last Edit: May 05, 2010, 04:42 pm by guns22 Reason: 1
I did see something about disabling DTR in perl while googling, but couldn't find anything relevant to php.

I may check out perl, though i know nothing about it.

I didnt know anything  about php till yesterday though lol. So i'll check your script, and see what i need to use perl.

Thanks much, i'll let you know if i end up switching over, or if i find another fix.

EDIT - What language is that? so i can try to have it translated :)

EDIT #2.
Right now, i send a request for data to the arduino, then i receive it, im also sending some other commands to it via php as well, some inputs.

Something i was thinking about though, if/when i scale this up, to more communication and variables, i was wondering if i i will need to switch to a stand alone program monitoring and sending the data to the arduino, with a database inbetween that program and php side of things.

Im truly brand new to all of this, so im just thinking outloud at this point.


May 05, 2010, 04:58 pm Last Edit: May 05, 2010, 04:59 pm by adalgisio Reason: 1
I tried to disable DTR either through PHP calling a shell (with stty -F) but nothing to do...it seems a limitation of PHP5...

The language is italian.

Which are your needs? What you have to do exactly?

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