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Topic: Regression between uno and uno R2 VALIDATED. HARDWARE PROBLEM CONFIRMED (Read 27 times) previous topic - next topic


Sorry if this is seen as a repost, but after wandering around it seemed that this section was more appropriate.

We have been getting problems recently with arduino boards.

We use I-wire on pin7 for some ibutton reading and had the arduino R2 halting immediately on powerup. Pressing the reset button once after it hanged makes it boot correctly.
We finally found that simply taking a 4.7k resistor from the board 5V to pin 7 causes the problem. On original UNO, this works.

Can you reproduce? (we can, each time, using any program, even 'blink') I have been trying on about 8 of the 40 i have in the office and all hang on startup with the resistor. I'm wondering if it's a design problem or just the serie.

Has anyone got any idea on what causes this behavior and how to solve it?

Thanks a lot.


Sorry if this is seen as a repost, but after wandering around it seemed that this section was more appropriate.

If you remove the other thread no one will complain :)
Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)


yes, certainly.

Does that mean that this place is more appropriate? I'm willing to kill that thread instead if i'm at the wrong section...

I would really love to have answers on this as i have to send prototypes pretty soon and i have no R1 to make everything work.

robert rozee

this would seem to be pin 13 on the 328p, port D bit 7.

the problem could be that this pin has an alternative function during startup, which is inconsistent with it being pulled high. a simple solution is that the pin has an option to be configured with an INTERNAL pullup, and to make use of that feature. ie, once your code is running, configure the internal pullup instead of making use of an external one.

this doesn't trace down the initial problem, but does provide you with a simple workaround.

rob   :-)



Problem is that programs don't even run. i don't know at the moment if it hangs at the bootloader or even before.
As no led blink, i think it's before bootloader starts.

R2 ought to have changed only hardware, as far as i've seen. What bothers me is that original UNO works and i don't feel i do something nasty.

Hanging up a system with just a resistor looks serious enough. I wished i could get more attention from the arduino team.
Do they come here at times, or is there an other place where to expose this problem?

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