REALLY weird errors happening, can't figure out why.

Hey all, I've got a ProMini that I'm trying to use for a transmitter to a quadcopter. Right now I'm still trying to get the test software to load up so I can even see if the pots on the transmitter are sending data to the mini. I'm using just a basic sketch to test the data input by printing the data values to the serial monitor. I'm using an FTDI adaptor to connect to the computer.

Here's where it gets really weird. When I have the system plugged into my computer, my mouse cursor starts going crazy. It will move in little jerks and twitches down to the very bottom left of my monitors. When I do manage to get it to do what I want, I get this error:

avrdude: ser_open(): can't open device "\.\COM4": Access is denied.

can anybody tell me what is going on? I'm relatively new to the mini, but I've used the UNO quite a bit and had no problems.

Sounds like your mouse might have the same FTDI adaptor. When the mouse is working properly, the port is taken so avrdude can't open it.

When your project does manage to connect, your computer is interpreting your board as the mouse and moving accordingly.

If I were you, I'd buy a different USB to TTL converter, perhaps one based on the CP2102 IC.