I am writing an application to control a Modem via USB Virtual COM port on Win7, WinXP, MAC OS X and Linux (command line).
I am using a K40 and I can successfully run the Virtual COM port using the CDC Class on Win7 64Bit PC. There are some little communication problems related to buffers but I it's basically working. I connected the TX and the RX to an internal UART of the MCU and all works.
The problem raises when I try to use the Virtual COM port on MAC OS X. The device is recognized as "tty.usbmodemxxx" when I try to send/receive any byte it the ZTerm (used for testing purposes) returns me that the USB Port is busy/not available. If I use a FTDI USB to Serial Converter it all works fine.
Againthe tty.usbmodem device is recognized but the PORT is always busy/not available while the same code ran in stand alone on my proto board is working on Win7.
Anybody had the same problem or can either point me to a working part of code to make a Virtual COM aka serial converter working? I know this can be considered a commercial stuff but any help will be highly appreciated.
Did you ever figure this out? I'm running into the same problem with a Kinetis K21.The CDC device works fine on my WIn7 machine but i'm getting a "Resource busy" error when opening the device with screen or minicom in OSX. I've verified that the file node is not opened by any process with lsof.