Virtual COM port MAC OSX Kinetis K40

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Virtual COM port MAC OSX Kinetis K40

Contributor I

Hi Guys,

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.


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Contributor II

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.


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Senior Contributor II

Jan Axelson's USB Forum is where many of the USB gurus of the world hang out.
They maybe able to help with descriptor issues, or OS Issues.

They probably can not help a lot with Kinetis issues.

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