To configure minicom(1) open terminal and type
$ sudo /opt/local/bin/minicom
or
$ sudo /opt/local/bin/minicom -s
Type CTRL-A-Z for configuration menu and help.
Type CTRL-A-P for Comm parameters
Usually 9600 8N1 is a good configuration for most serial communication.
Type CTRL-A-O for minicom configuraion.
Choose Serial port setup then “A” to configure the Serial Device.
If your RS-232 adaper is the keyspan one, the device name will look similar to this one:
/dev/cu.USA19QW3d1P1.1
This depends on which USB port you have connected your adapter.
For PL-2303, the device name will be:
/dev/cu.usbserial
Save the configuration. Now your minicom(1) should be working fine.