Bricked UNO board?

Hi, I'm playing with UNO R3 clone board. Everything worked perfectly but I can't upload new program now. I'm using Ethernet shield, DS3231 module and DHT11 in the current project.

I don't know why and how, but Arduino refuses to accept new program since yesterday. I have disconnected everything and did a loopback test - it works fine.

When I connect USB to the board, both green and orange (13) LED immediately shine. No blinking visible. If I press reset button, nothing happens. The orange LED does not turn off, it shine all the time.

Programming output ends with: avrdude: Send: 0 [30] [20] avrdude: Send: 0 [30] [20] avrdude: Send: 0 [30] [20] avrdude: ser_recv(): programmer is not responding avrdude: stk500_recv(): programmer is not responding

I do not have any other working board, no programmer. I have USBtoTTL converter and Pro MINI which I never used so far.

Any ideas? Thanks

Your bootloader is crashed. Upload the bootloader again using avr Pocket programmer.

Add one more possible cause for non-responsive boards: if screws are used to attach the board to a chassis of some sort, the screw can short out a part of the board.

After attaching an Uno to a chassis with four 4-40 socked head screws with teflon standoffs, the board would no longer respond to resets, and the 'not in sync' message would appear when uploading programs. Loosening the screws allowed proper operation. It didn't take much pressure to cause the short.

The most common cause of "bricked" Arduinos is having loaded a program that hogs serial. Try pressing reset just before unloading.

Thanks, it was the bootloader problem. I have used AVR pocket programmer to fix it.

For future reference - Connect bricked arduino to pocket programmer and the programmer to USB port. Open Arduino app, select Tools - Programmer - USBasp and then Tools - Burn Bootloader.