Below is a 100 % sketch-free way to prove the Arduino IDE (or your PC) can talk to the HexBright before you ever hit “Upload”.

1. Open the Serial Monitor (the only thing you need)

1. Plug the HexBright in (USB).
2. In Arduino IDE: Tools → Board → HexBright
3. Tools → Port → COMxx (HexBright) (or /dev/cu.usbmodem… on macOS)
4. Click the magnifying-glass icon (top-right) → Serial Monitor.
5. Set baud rate = 9600 and line ending = No line ending.

2. Send the “?” query command”

The HexBright bootloader responds to a single ? byte with its signature string.

1. In the Serial Monitor input box, type exactly:

   ?
   
   

2. Press Enter (or click Send).

Expected reply (within 1 second)

HexBright Flex v1.0

or similar (HexBright + version).

You will see it appear in the monitor window.

That’s it – no sketch, no upload. The PC → USB → ATmega328P → bootloader round-trip is verified.

3. Alternative: avrdude from the command line (still no sketch)