All, Something has changed in 15.4 related to access serial devices over USB in 15.4 and I can't figure out what? Here is the setup. I have several microcontrollers I connect to my laptop over USB. (TI MSP432 and RM46). In 15.0 after saving the connection parameters as root, I could connect to the devices on ttyACM0 as my normal user. However in 15.4, minicom refuses to connect saying can't get a lock on ttyACM0. (if I run minicom as root, then it works just fine) This has other implications as well. I use TI Code Composer Studio as the IDE for the microcontroller code. It provides arm versions of gcc, clang and the TI compiler. It also needs to connect over ttyACM0 to update the XDS110 debug probe firmware and to flash new programs to the microcontroller's flash memory. This worked seamlessly as user in 15.0. It now cannot update the firmware or flash new programs to the microcontrollers (see error at end) I suspect this may be a group issue. In 15.0 there was the adm group GID 485, that I made myself a member of. (I'm not positive this is the group at issue, but...) The adm group is not present in 15.4. Is this the culprit? All other groups seem to be common between 15.0 and 15.4. If not the adm group -- what else could it be? I had no issues using ttyACM0 as my user in 15.0 and now in 15.4 it seems I lack some type of permission to use it. The error thrown by CCS is: CS_DAP_0: Error initializing emulator: (Error -260 @ 0x0) An attempt to connect to the XDS110 failed. The cause may be one or more of: no XDS110 is connected, invalid firmware update, invalid XDS110 serial number, or faulty USB cable. The firmware and serial number may be updated using the xdsdfu utility found in the .../ccs_base/common/uscif/xds110 directory of your installation. View the XDS110SupportReadMe.pdf file there for instructions. (Emulation package 9.7.0.00213) I'm connected to it in an xterm watching the output of a MPU9850 update at 100 HZ right now -- it's connected and working (this rules out a faulty USB cable as well). The firmware update is also fine. So it looks like the same permission issue with can't get a lock on ttyACM0 that minicom complains of. -- David C. Rankin, J.D.,P.E.