Hi I have been having communication problems using the usb ttl link, this was also true downloading using the Arduino, but as I have an AVRISP I used the Arduino to compile and the AVRISP through ATmel Studio to download the complied file and did not persue the problem. With Pronterface not comminicating I had to persue the issue, it transpired that access was denied (Error 5) so I checked theby Derek - Experimental