I am completely new to Ultratronics Pro board, just purchased it and installed Repetier Development Firmware from this link https://github.com/repetier/Repetier-Firmware/tree/development
I had no issues compiling and uploading the sketch and I can communicate via programming port USBP (detected as COM4), but when I try to connect via regular USB port, Pronterface shows the following error:
[ERROR] Could not connect to COM3 at baudrate 115200:
Serial error: could not open port 'COM3': WindowsError(5, 'Access is denied.')
Meanwhile Windows detects the port correctly as Arduino Due (COM3). Do I need to change anything in configuration files to activate non-programming USB port? I've tried enabling Bluetooth, since it also uses serial communication, but that did not help.
When connected to Octoprint, I get error "Error: SerialException: 'device reports readiness to read but returned no data". USBP is working fine.
Thanks