Minicom is installed by default on Debian microSD. To run it from the shell prompt just type:
~# minicom -s
-s parm runs minicom in setup mode.
Select Serial port setup and type [enter]:
Now type [A] to change the serial port and [F] to disable the hardware flow control. Select Exit from the configuration menu. Now each character press on your keyboard is sent to the selected port and each character received from the serial port is print on the screen.
Type [CTRL-A] and [Z] for more help on Minicom.
By default the serial port are not accessible to the normal users, so when you run minicom we get a permission denied error.
Check the permissions to the serial devices by typing:
$ ls -ls /dev/ttyS* /dev/ttyU* ... 0 crw-rw---- 1 root dialout 188, 0 Jul 8 05:18 /dev/ttyUSB0
then add your user name the dialout group to enable it to access to the serial port by typing:
$ sudo usermod -a -G dialout username
Check now which groups the user belongs to:
$ groups username username : username adm dialout cdrom sudo dip plugdev fuse lpadmin sambashare
Logout from your Linux session. Login again and try to launch minicom directly without using the sudo directive.