How do I find out if something is using the serial port?

I want to program a microcontroller under Debian Wheezy, but can't get it to work so far. I asked on Electrical Engineering and got the advice to check if something is already occupying the serial port. I don't have the program they suggested, brltty.

How can I check if there is some other package preventing the microcontroller board from talking to the computer? Or if there is some kind of driver problem with the device?

This is what happens when I plug it in:

rumtscho@simak:~/Projects/had_launchpad-blink-master$ dmesg | tail
[11936.051300] usb 4-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[11936.051306] usb 4-1: Product: Texas Instruments MSP-FET430UIF
[11936.051313] usb 4-1: Manufacturer: Texas Instruments
[11936.051318] usb 4-1: SerialNumber: 95FF469286C9572A
[11936.060401] cdc_acm 4-1:1.0: This device cannot do calls on its own. It is not a modem.
[11936.060412] cdc_acm 4-1:1.0: No union descriptor, testing for castrated device
[11936.060467] cdc_acm 4-1:1.0: ttyACM0: USB ACM device
[11946.113517] generic-usb 0003:0451:F432.0005: usb_submit_urb(ctrl) failed
[11946.113550] generic-usb 0003:0451:F432.0005: timeout initializing reports
[11946.114261] generic-usb 0003:0451:F432.0005: hiddev0,hidraw0: USB HID v1.01 Device [Texas Instruments Texas Instruments MSP-FET430UIF] on usb-0000:00:1d.0-1/input1

Can I somehow troubleshoot the connection from here?