USB serial miscommunication

Hi, I have written an app for my raspberry 3 that manipulates strings received from a gps via the GPIO serial port on ttyS0. That works as expected.
Now the problem is when I use a USB to ttl converter and connect the gps to the converter and plug the converter into the usb then my app does not work anymore. I have changed ttyS0 to ttyUSB0 as when I write [quote]cat /dev/ttyUSB0 [/quote] then I can see the gps output strings updating continuously.

Could the problem be with XOJO?

It could be the serial port is in use.
Or you may have the wrong one. USB to serial converter should work out of the box.

Check the permissions of the device under dev (/dev/ttyUSB0) it must be

-rw-rw---- root dialout

Also check the user pi is in dialout group

As last you can try the Xojo program as root (not recommended, of course, but only to test if is a problem with permissions)

Also can use:

sudo lsof /dev/ttyUSB0

To check if the device is used by other program