Hu Sun replied to the topic 'Port is already used error' in the forum. 6 months ago

you are a genius´╝üworked for me like a charm for me. I am having exactly the same chip in my USBTTL cable.

Scratching my head for a day, and even teared apart my az gti to check connections, and ripped off the cable to test the if the cable itself worked or not.

I guess ppl having this issue may have got the USB TTL cable ID conflicted with udev rules already in place.