I was playing with a sketch that takes readings from I2C magnetometer and printing them to serial.
At some point it stopped sending data back. Resetting the board didn't solve the problem.
Since then any attempts to upload program lead to "avrdude: stk500_recv(): programmer is not responding".
Power LED is always on, and RX blinks when upload attempt starts.
I tried loopback test and it looks fine so usb to serial correctly.
5V and 3.3V seem to be ok on respective outputs.
L LED doesn't blink after reset and looks to be in input mode (dim light).
Checked that correct board/tty is chosen in the menu.
What are my investigation options? Should i try getting another board and burning a bootloader or something could still be done without additional hardware?
I would suggest first to just purchase a replacement 328P chip with Uno bootloader already installed in it, should cost less then $6 or so and is always useful as a spare or use in a standalone circuit. If installing the new chip solves the problem then you can take steps to see if you can do something with the original chip such as trying to reburning the bootloader.