Hi,
great you found a solution! For my board it doesn't work, but also the reset button never has worked before. I guess I have to get a new one, then I`ll try it again!
Vile
Hi Martin,
excellent and bvery very practical solution. could you please tell me about capacity of the capacitor you used? many thanks, reha
Hi all,
I soldered 1uF tantal capacitor as Martin mention btwn pins of the reset switch and it works ! reha
Hi all,
another update.. As Martin mentioned that "if you are using many shield on this board, you also need to add a capacitor for each shield's reset switch.".. I need to update my response as..
1uF capacitor is sufficient for "board only". But when I connected my SDMemory card to board, I needed to increase capacitor to 4.7uF...
Hi! I am using 10uF/10V capacitor for my board. My arduino board is connected to iteadstudio's motor shield and Arduino Ethernet shield.
Friends,
I need to update the capacity values that I shared yesterday. Yesterday, 1uf/4.7uF capacitors had been worked. But today I noticed that "some of the boards" (most probably I purchased them from different manifacturer" need even bigger capacity.. I used 10uF/10V capacitor (like Martin did) .. they are working normally.. reha
Hi,
I tried it with 2,2uF and 4,7uF and both did not work on the DUE only, no shield or periphery. So it seems to be related to my specific board (as I said the reset button is not working). In a few days I can test it with a new Arduino DUE.
Vile
Hi Vile,
could you please try 10uF also? As I mentioned above, some of the boards did not worked with smaller capacity of condenser.. good luck. reha
Hi,
it seems to work with a 10µF cap, although the RESET button is defective.
Also I received today the new DUE board I purchased. Using a 10µF cap also works. I will do some other tests with longer power off times. They are both DUE R3 (not -E), but the newer one (HIMAYALA basic DUE Board Arduino DUE kompatibel 4060137002403 | eBay, more expensive than from china, but fast shipping) has a much better soldering quality.
Hi Vile,
great news.. please keep us updated (with longer off time).. reha
I made some measurements with a scpoe. As the reset button simply pulls the signal down to GND, the cap just delays the rise of the reset voltage, so for the first 100 or 200 ms it's like you press the reset button. That means it takes this amount of time until the code runs, but IT DOES 
I don't know, maybe it could cause some long term problems if the reset button is used often, because it shorts the capacitor which causes high currents for a short time, but I think this is no problem since the DUE finally runs nice.
This is what happens without any capacitor:
This one zooms in, look at the time/div:
And this happens using a 10µF cap in parallel to the button as reha posted:
I'd be cautious to hang big cap on IO pin, the problem may come during powering off, if cap discharged to input pin, it may inject enough current to latch-off IC. I can't find anything in atmel's "design board suggestions" appl note regarding limits on cap, but 10 uF looks too big on my view. DS says 10 nF. For higher value resistor in series with cap may be necessary.
Hi guys,
universal answer for this issue is MCP120/130-300 which is voltage watchdog and ensures correct RESET signal after power voltage is stable. I tried also solution with 10uF capacitor and it does't work for my DUE clones for some reason. MCP120-300 costs around 0.3EUR and is available in SOT23 package. It can be easily soldered to the bottom layer of DUE between pin RESET and 3.3V and GND. See datasheet for details and you will understand quickly and clearly. From the time I started using MCP I sleep really well. BR, Petr
Petr,
many thanks for sharing.. in order to avoid any misunderstanding, is it possible to share photo of your connection? reha
Hi again!
Enclosed you will find the photo of MCP soldered to bottom layer. Please note that MCP package is upside down to fit right pinout! Just solder it between RESET and 3.3V and find closest ground and "draw" track or use small piece of wire to connect Vss pin of MCP with GND of DUE.
I usually use MCP on my own shield boards, so I don't need to place it as shown in the picture. For example, when using Ethernet shield, MCP can be easily soldered on its top layer. I hope, guys you will cope with this somehow.
Sorry for picture quality, making photo is not my hobby, making miracles with arduino definitely is. Have a nice day!
BR,
Petr
Hi guys, I use 2 resistor 10k and 1 cap 220uF to fix this problem in my project. Hope it helps.
Hello!
Just use the datasheet, ch 16: Supply Controller.
This is a fine tunable beast of a Reset Controller. Question is: what is causing the behavior?
Could anyone with the problem scope clock generation, 3,3V vs. core voltage?
Strange...
Yours
Andi
My Problem is only remotely related, sorry, following story:
I had, on some poor chinese saintsmard red due, the problem that no Reset would occur when uploading, so I had to press reset button at just the right time. Since I want to do Arduino and robotics with kids, and they will (hopefully) be using matlab/simulink target library (Matlab Coder is underlying technology, free in student version for Arduino, NXT/EV3 Lego Mindstorms, and Raspberry Pi) to let Matlab do the programming, this is not the way to go 
I measured the reset signal that the ATmega16u2 gives out on Pin18 via R18 to master_reset.
This Resistor is given with a value of 1kOhm for the schematics from arduino.cc .
I found some residues of the soldering process between ISP headers on backside to via of Reset line. Perhaps this was enough to make the thing refuse to reset?
Now I attach a foto of my scope picture of the double reset into boot loader.
I will try to capture one with the new 1k Ohm resistor soldered on top of the old (10k) one.
I used my old Weller WECP-20 soldering station, freshly repaired, with the pointiest tip I could find.
Still I wish I could steady my hand with some glue or tape
Soldering paste was of help, but I always fear I spill it around, and it would creep under the ICs etc...
I put some pL with a needle tip on the contacts of the old resistor, then held the new one in place and heated up with soldering iron tip. Gave it one more tiniy bit of soldering paste, heated again...
Best thing would be heat radiation just for such a tiny spot. But well.
Then I measured the outcome directly on Pin22 of 16U2 to the Pin Header RESET.
0,918 kOhm.
This is ok for me
I had the same problems with my SainSmart DUE. I don't know witch revision it is, but it has already the IOREV and the unused pin near the reset pin.
My solution might be better then directly connecting a 10 µF ceramic or tantalum capacitor to the reset switch. That will damage the switch over time and is a risk for the clamp diodes in the microcontrollers.
I connected a 10 µF electrolytic capacitor (ceramic or tantalum should also work) with a 470 Ohm resistor in series between the reset pin and ground. This will delay the startup of the SAM by around 150 ms, as you can see below. The current through the reset switch (and maybe other parts) is limited to 7 mA by the resistor, so nothing can be damaged.
Sorry for noisy environment CH1 is measured at the reset Pin and CH2 between the resistor and the capacitor.
I assembled the two parts on my prototype board, together with some other components. But it will also be possible to solder them (as SMD) direct to the switch.
This solution is well tested. The reset switch works as before, also the automatic reset during programming via programming port. I tested the startup of the SAM in time steps from 1 to 5 minutes off-time and encountered no problems anymore, also a start after a night works probably. So there should be no long time issues as well.
I hope this solution helps all people with the same problem.
Greetings from Germany,
Bimbo385
yo Bimbo385,
your solution works perfectly!
cheers!
bimbo385 and earx
You can show a picture of changes in your board ?
thanks !