Hey guys, really odd problem here. I have an Arduino Uno R3, brand-new, that functions but can't get new code over serial.
When I try to upload a sketch over USB, I get one of these errors:
avrdude: stk500_getsync(): not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
TX and RX LED's briefly flash. Occasionally, the L and/or TX LED's stay on.
The odd part is that the Arduino seems to be fully functioning. I can still upload sketches with ICSP, and UART over USB does work.
I tried using DFU to refresh the 16u2, burned fresh firmware on the 16u2 over ISP, burned new firmware on the Mega328 over ISP, and even pulled the Mega328 and replaced it with a known-working chip from another Arduino. No dice.
Any suggestions or troubleshooting tips?