The COM port is being used by another software application or the driver is corrupt.
: If it's a work-related issue, consider consulting with a colleague or a professional who has experience in the relevant field. est3 sdu software link
A proprietary or specifically pinned serial cable designed to interface between the standard DB9 male end of your adapter and the 3-CPU programming header. Configuring the SDU Communications Port The COM port is being used by another