HowTo

Before starting, note that these functions are intended for use on Windows PC only. 
Required Microsoft Office applications (Excel, Word) should be installed on the PC. 
Functions will not work with Online Office versions such as Office 365, Outlook etc. 

Macros must be enabled and documents should be saved as type Macro-Enabled. 

An 'intermediate' or better level of VBA and serial comms knowledge is assumed. 

Functions were developed on Windows 10 (64-Bit) and Office Professional 2019 (32-Bit).
Tested on Office Professional 2016 (64-Bit) and Office Professional 2019 (32-Bit).
Usage with other Windows and Office versions is untested.
Follow testing steps below to check compatibility. 

Host PC should have a physical or virtual COM Port available for use. 
COM Port 1 shown - change (1) below to another COM Port if required. 
Check/Edit COM_PORT_MIN and COM_PORT_MAX values in SERIAL_PORT_VBA.
Testing requires a second device to be connected to this COM Port.

1.  Download SERIAL_PORT_VBA.bas to a known location on your PC
2.  Open a new Office Application (Excel,Word,Access) document 
3.  Enter the VBA Environment (Alt-F11)
4.  From VBA Environment, view the Project Explorer (Control-R)
5.  From Project Explorer, right-hand click and select Import File.
6.  Import the file SERIAL_PORT_VBA.bas
7.  Check that a new module SERIAL_PORT_VBA is created and visible in the Modules folder. 
8.  Close and return to Office application (Alt-Q)
9.  IMPORTANT - save document as type Macro-Enabled with a file name of your choice.
10. To test, another PC, terminal or similar device should be connected to the host PC's COM port.
11. Re-enter the VBA Environment (Alt-F11)
12. Select the VBA Immediate Window (Control-G)
13. Enter the following commands in the Immediate Window :-
14.   ?debug_com_port(1)    
15a.  ?start_com_port(1) to use default COM port settings  - or - 
15b.  ?start_com_port(1,"Baud=9600 Data=8") to specify COM port settings
16. Check that debug information is shown and the last line indicates SUCCESS
17. Send some text to your device from VBA e.g. 
18.  ?transmit_com_port(1,"Hello Device")
19. Check that 'Hello Device' is received correctly on your device
20. On your device, send some text back to VBA - e.g. Hello, Word !
21. Receive the text from your device back to VBA
22.  ?receive_com_port(1)
23. Check that Hello, Word ! is displayed correctly in the Immediate Window
24. Assign some text to variable Y in the Immediate Window
25.  Y = "HELLO DEVICE 123"
26. Send variable Y to your device and check that it is received correctly
27.  ?send_com_port(1,Y)
28. On your device, send some more text back to VBA - e.g. QWERTY 
29. Receive device text into variable Z
30.  Z = receive_com_port(1)
31. Display variable Z and check if text received correctly
32.  ?Z
33. Optional - explore other Public functions, e.g.
34.  ?wait_com_port(1)
35.  ?check_com_port(1)
36.  ?put_com_port(1,"A")
37.  ?get_com_port(1)
38.  ?device_ready(1)
39. Close the com port
40.  ?stop_com_port(1)
41. Optional - repeat above steps without debug messaging 
42.  ?debug_com_port(1) again to toggle debug off. 
43. Optional - explore EXAMPLE function at end of VBA Module.

Public functions can be incorporated into your own VBA programs.
Where appropriate, Public functions can also be used directly in Excel worksheet Cells.