Module: ft991utility.py
 
 Introduction
 ------------
 The ft991 utility is an interactive tool for backing up and restoring both
 the memory settings and menu settings of the Yaesu FT991 transceiver.
 Individual memory locations store information about frequency, repeater
 offset, signaling, tags, modulation, and clarifier.  Menu settings store
 configuration information about current menu options and parameters.  The
 utility also has a pass through mode for sending CAT commands directly to
 the transceiver.  This feature is useful for future code development and
 debugging.
 
 The ft991.py module encapsulates the FT991 CAT commands and handles low
 level serial communication to and from the FT991 usb port.  CAT commands
 are encapsulated according to object oriented methodology, that is, 'set'
 to send parameters and settings to the FT991, and 'get' to receive status
 information back from the FT991. Additionally ft991.py contains helper
 functions for parsing data read from backup files. The 'set' functions
 also handle formatting of CAT commands and their associated parameters,
 while 'get' functions handle parsing of data returned from CAT commands
 that return status information.
 

 Email bug reports and comments to: ka7jlo@gmail.com

 Notes
 -----
 1. The files ft991utility.py and ft991.py should be downloaded from the

    github repository and placed in the same folder.

 2. Before running the utility you may need to edit line 39 or line 40 in
    the "environment setup" section of the file "ft991utility.py".  Be sure
    the com port is correct.  This will depend on whether you are running
    Linux or Windows and on the default serial port assigned to the FT991.  
 3. To run the utility, open a terminal session in directory containing

    the ft991utility.py and ft991.py files.  Then simply type the utility
    file name after the command line prompt, e.g.,
        ~$ ./ft991utility.py
    If necessary, change the permissions on ft991utility.py to allow the file

    to be run as an executable.  To change the permissions on Linux run the
    command
        ~$ chmod +x ft991utility.py
 4. Windows users will need to have the python 3.8 framework installed.

    Probably, the easiest way to get the framework is to install the
    Windows Subsystem for Linux Ubuntu platform.  Note that the utility

    has not been tested on Windows and the developer makes no guarantees.
 5. While it is possible to run the utility completely from the command
    line using command line options, beginning users are encouraged to use
    the interactive mode.  To use the interactive mode simply type the file

    name of the utility with no command line arguments, e.g.,
            ./ft991utility.py

 6. The utility saves memory settings in a comma-delimited file that

    can be imported into a spreadsheet application for ease in viewing

    and editing.
 7. The verbose mode, available both as a command line option and in

    interactive mode, echos raw commands sent to the FT991, as well as
    raw status returned by the FT991.  This feature is useful for development
    and debugging purposes.

 8. If you already have repeater frequencies and such programmed

    in memory, you should first run the 'bm' command in interactive mode
    to back up your current memory settings.  Unless you change the default
    file name, this file should appear in your current working directory as
    'ft991mem.csv'.  Change this file name to something else such as

    'ft991mem_todaysDate.csv so that you can restore from this file at a

    later date if necessary.

 9. By the same token you should immediately back up your menu settings using

    the 'bu' command in interactive mode.  The default file name is
    'ft991menu.cfg'.  Likewise change this file name to something else.

 10. The example file 'example.csv' shows how a memory settings file should
     appear.  To load these settings in your FT991, run the 'rm' command in
     interactive mode.  When prompted to enter a file name type 'example.csv'. 
     For example,
         Enter file name or <CR> for default: example.csv
 11. Backup and restore of VHF/UHF split frequency repeater settings is not
     supported by the FT991.
 12. Please do not edit the menu settings file unless you absolutely know

     what you are doing.  There should rarely be a need to edit this file.
     Menu changes should be made on the FT991, itself, and then backed up.