← FAQ

“Access denied” or “port busy” when opening a COM port?

1. Close other programs that may hold the port: other serial terminals, the Arduino IDE serial monitor, flashing tools, USB pass-through to a VM.
2. When opening fails, QCCOM’s error message names the program that holds the port, so you know what to close.
3. Unplug and replug the device if the driver is stuck.

Flashing without closing the log

When a command run in the QCCOM terminal panel uses the open port (e.g. esptool.py -p COM3 write_flash … or idf.py -p COM3 flash), QCCOM closes the port first and reopens it when the command finishes, waiting for the device if it re-enumerates.