Serial Port Already in Use - MacOSX Lion

I have purchase a makey makey board and I am trying to upload Arduino code onto it from my macbook air running OSX 10.7.5.

I when I try to upload the code i get the following area message that my serial port is already in use...

processing.app.SerialException: Serial port '/dev/tty.usbmodem1421' already in use. Try quitting any programs that may be using it. at processing.app.Serial.touchPort(Serial.java:119) at processing.app.debug.AvrdudeUploader.uploadViaBoot loader(AvrdudeUploader.java:203) at processing.app.debug.AvrdudeUploader.uploadUsingPr eferences(AvrdudeUploader.java:67) at processing.app.Sketch.upload(Sketch.java:1671) at processing.app.Sketch.exportApplet(Sketch.java:162 7) at processing.app.Sketch.exportApplet(Sketch.java:159 9) at processing.app.Editor$DefaultExportHandler.run(Edi tor.java:2380) at java.lang.Thread.run(Thread.java:695)

can please explain how i fix this problem. I have been searching on the interwebs and just can't find a fix.

http://www.baldengineer.com/blog/2012/10/08/arduino-fixing-serial-port-in-use/

Thanks james for the link. I'm using WIN7 X64, faced same issue. Sometimes the IDE says Access to COM PORT X denied: I used to unplug & replug the arduino board for solution, are there any proper fix for this? One more thing to know, Is PL2303HX able to upload sketch in arduino? I have one. tried but no success. Even installing the driver took ages. Any solution for 2303 chips?

nightcrawler218: Thanks james for the link. I'm using WIN7 X64, faced same issue. Sometimes the IDE says Access to COM PORT X denied

It means something is holding it open, maybe avrdude hasn't closed the port yet. I don't know enough about Windows to know.

nightcrawler218: Is PL2303HX able to upload sketch in arduino?

These chips are fincky. One probably is that the "reset" pin on many modules (especially those found on eBay) isn't connected to DTR and RTS, which is what initiates the arduino's Auto-reset.

If you search the forum and the web for PL2303 you'll find people who have tried.

I get the the PL2303 from a cheap GPS device, both the modules are attached together to output the serial data via USB. It does its job fine but the issue occurs while uploading sketches. :roll_eyes: Thank you James.