#15 Mobilinkd NucleoTNC Fails to Connect at 38400 Baud

[Rob Riggs]

beta154 -- cannot open any TNC at 38400 baud. The Mobilinkd NucleoTNC operates at 38400 baud. Attempting to connect to the TNC at 38400 baud results in an exception (see attached screenshot).

Opening the TNC at 115200 succeeds. However, YAAC will only receive garbled data at that speed.

Similar problem is observed with a TNC3, which ignores baud rate settings. Connecting at 115200 succeeds, whereas 38400 fails with the same exception.

[Andrew Pavlin]

Please send the YAAC.out file from your configured YAAC log directory. Your screenshot showed only part of the error message.

[Rob Riggs]

Log file attached.

Relevant information seems to be:

Caused by: gnu.io.UnsupportedCommOperationException: Invalid Parameter
        at gnu.io.RXTXPort.setSerialPortParams(RXTXPort.java:211)
        at org.ka2ddo.yaac.io.SerialTNCConnector.configure(SerialTNCConnector.java:160)

Googling for "RXTXPort.java:211" returns a lot of results, many of the related to 38400 baud rate.

[Rob Riggs]

Note that termios(3) says this:

The actual bit rate corresponding to B38400 may be altered
with setserial(8).

After looking at the code, my hunch is that the termios struct is not zeroed out, leaving garbage in the custom divisor. When B38400 is passed, the kernel tries to construct a baud rate using the garbage in the custom divisor field and fails.

[Rob Riggs]

This seems to be a potential fix for the issue.

https://sources.debian.org/patches/rxtx/2.2pre2+dfsg1-2/usb_38400.patch/