Hello! Running Mint 18.3 (Sylvia) with FLDIGI for linux, using /dev/ttyUSB0 external soundcard and /dev/ttyUSB1 serial converter for transmit/receive switching.

UZ7HO's soundmodem/easyterm Windoze program for packet radio runs successfully on a separate linux laptop using internal soundcard and USB serial converter for T/R with VHF radio. I know this works!

On my Mint tower, FLDIGI runs fine. UZ7HO soundmodem requires that T/R switching addresses 'COM' ports as it is a Windoze program. I created a soft link 'COM1' to my /dev/ttyUSB1 successfully on the laptop, so I did the same on the tower.

On the tower, FLDIGI still runs fine (both RX/TX). Soundmodem also receives packets fine from my HF radio, however, after typing text and hitting 'ENTER' for transmit, soundmodem/easyterm locks solid. A small window opens with the error message,

'Error Opening Wave Output Device [device already allocated]'.

To clear this I must kill the programs PID. I have re-booted the machine and tried from fresh boot with soundmodem/easyterm with the same result.

My desire, of course, is to be able to access both USB devices (soundcard and serial control) from either FLDIGI or WINE>soundmodem/easyterm - but never at the same time ;-}

Well - the above mentioned error message resulted from the windoze program not addressing the proper sound card. The configuration pointing at the USB sound was not maintaining persistence. After scrutinizing the setup screen and then touching the config file directly, that is fixed ...

Now when text is entered and 'ENTER' is struck, soundmodem appears to be working; outgoing audio is going to the USB soundcard. The T/R switch is still not responding via the USB-serial convertor. Still working on that.

I had failed to mention that besides the above, I have another USB/Serial converter that connects the computer to a packet TNC for VHF. Both converters are the same manufacturer and model.

I had an inspiration so removed my link to ttyUSB1 and then created two links; COM1 to ttyUSB0 (to NOT be used) and COM2 to ttyUSB1. Now finally, the soundmodem program addresses COM2 correctly and works.

Both minicom (VHF) and fldigi (hf) programs also work; properly addressing the correct ttyUSBx devices.

Sorry to have chewed up space, thank you to LinuxQuestions, and just maybe this will help the next guy!