based on this project http://arduino.cc/forum/index.php/topic,1357.0.html
in this part "On PC side, APC220 is communicating with Windows on serial COM port, so we can use Arduino's software as serial platform. As we are not talking to Arduino on this software this time, change of serial port is needed. In "Tools" -> "Serial Ports", select the COM port used by the APC220(the one with USB adapter connected to PC). Then click "Serial Monitor", type "A" and send, signal will be sent from PC to Arduino through the APC220 modules."
I got this problem " serial port 'COM7' already in use ".
how to solve this? anyone expert can help