please read and answer! it's very important

Hello, I've bought my arduino uno last month and it was so good. Yesterday while i was loading my program on the Arduino uno appeared this message:avrdude: stk500_recv(): programmer is not responding. I checked that in the tools i chose the right type of arduino, and it was ok. The problem is that the usb modem ports are disappeared. I tried with a new arduino and it was all ok. I was working on a mac with OSX 10.9.1 Mavericks. I tried to load the program on the arduino from a W7 computer, but it didn't recognize at all the arduino and when i tried to load the same and late a different program appeared this message: stk500_getsync(): not in sync: reap=0x00.

i hope you'll help me!!

Thomas Civiero from Italy

i've also tried whit a different cable and version of the IDE.

This sounds like the problem I am having, but this is my first board and my first time with an Adruno product, UNO. Got it from Amazon. I just tired plugging it into another computer running XP and it gave me the same response, no comport assigned, it comes up in Device Manager as an Unknown Device. So how do we find out if these are bad boards? Mine says it was made in Italy too.

Try the Loop Back test.

Is your sketch suddenly outputting a lot of data on D0/D1 and flooding the USB output so the PC cannot communicate? Try this - press & hold the Reset button, download a simple sketch (blink), release the reset when the IDE shows "compiled xxx of 32xxx bytes". Turning on verbose outputs under File:Preferences can make finding the right time to release Reset easier.

it doesn't work. if i change the CPU (ATmega328p-pu) will it work normally?

If you can't get loopback test to work, the USB/Serial chip is not working. Changing the microcontroller will not help.

i did the loopback test but the pc didn't recognize the arduino board (i've collegated the reset pin with the ground and the rx with the tx) . What i can do to safe my arduino?

I think one of my Unos (maybe both) has a poor female USB connector as it sometimes appears to lose contact with the PC - possibly if I have accidentally tugged the cable. Pushing it in sorts the problem out but, of course it then appears as a different connection. Maybe it would be worth while fiddling with your cable / Arduino connection. I'm using Ubuntu Linux.

...R

I was getting the same error as you. I am using Linux and somehow my comm port switched to /dev/ttyS0. I switched back to /dev/ttyACM0 and all is good. I know you are using a MAC OS, but maybe check your port? Good Luck!